TS  A local transition state search is performed directly after the successful saddlepoint interpolation.  
INT=Real  Reduction of interpolation distance in each saddle step. By default a 5% reduction (INT=0.05) is used.  
MAX=Integer  Maximum number of saddlepoint interpolation steps. Default is 100.  
TOL=Real  Interpolation distance tolerance [a.u.] for saddlepoint convergence. Default is 0.1 atomic units. 

The relevant atoms for the concerted rearrangement are C(4), O(5), H(6), C(1) and O(2) in the reactant and C(13), O(14), C(19), O(20) and H(22) in the product structure. To ensure that the alignment algorithm maps these atoms correctly onto each other such that the saddle interpolation follows the concerted reaction path, they are numbered accordingly in the structure definition of the reactant and product.
VXCTYPE PBE SCFTYPE MAX=500 SADDLE INT=2.0 MAX=200 # # Optimized reactant coordinates # REACTANT CARTESIAN ANGSTROM C1 1.146304 1.580047 0.304830 6 12.011000 O1 1.474470 2.704811 0.094272 8 15.999400 C 1.478037 1.068974 1.680762 6 12.011000 C2 0.388141 0.637819 0.631850 6 12.011000 O2 0.381260 1.189947 1.947188 8 15.999400 H1 0.758490 2.097150 1.833935 1 1.007940 C 1.048313 0.421392 0.145352 6 12.011000 C 1.939655 1.366263 0.372306 6 12.011000 C 3.241408 0.952931 0.686023 6 12.011000 C 3.637166 0.375842 0.466195 6 12.011000 C 2.745608 1.314937 0.071382 6 12.011000 C 1.442073 0.907573 0.371235 6 12.011000 C 0.308225 1.703520 0.973142 6 12.011000 H 3.960249 1.673741 1.103430 1 1.007940 H 4.662742 0.682994 0.718950 1 1.007940 H 3.070566 2.354154 0.245424 1 1.007940 H 1.634675 2.414219 0.528049 1 1.007940 H 2.066621 1.836068 2.219392 1 1.007940 C 2.257501 0.257740 1.553539 6 12.011000 C 1.511818 1.286833 0.722868 6 12.011000 O 1.427834 2.455869 1.104029 8 15.999400 H 2.469807 0.701939 2.544632 1 1.007940 H 0.203258 2.717154 0.544618 1 1.007940 H 0.531868 0.883086 2.232117 1 1.007940 H 0.440534 1.793379 2.070772 1 1.007940 H 3.231445 0.055345 1.053604 1 1.007940 C 0.945955 0.847999 0.649669 6 12.011000 C 2.078732 1.028854 1.680712 6 12.011000 H 1.724896 0.679675 2.668085 1 1.007940 H 2.366493 2.098307 1.735541 1 1.007940 H 2.979948 0.434441 1.415635 1 1.007940 # # Optimized product coordinates # PRODUCT CARTESIAN ANGSTROM C 1.364437 1.346285 0.835797 6 12.011000 O 1.215160 2.555667 0.991251 8 15.999400 C 1.651005 0.332453 1.938566 6 12.011000 C 1.302791 0.639095 0.533580 6 12.011000 C 2.023969 0.959913 1.201220 6 12.011000 C 0.050517 1.093638 1.304525 6 12.011000 C 1.228417 0.650885 0.640377 6 12.011000 C 2.383053 1.445681 0.648124 6 12.011000 C 3.566686 0.978715 0.067793 6 12.011000 C 3.629589 0.297452 0.514493 6 12.011000 C 2.497068 1.106654 0.514108 6 12.011000 C 1.294672 0.632954 0.049150 6 12.011000 C2 0.102654 1.498701 0.041826 6 12.011000 O2 0.177817 2.735059 0.077486 8 15.999400 H 4.458601 1.622475 0.067957 1 1.007940 H 4.568591 0.652453 0.965774 1 1.007940 H 2.504895 2.117874 0.948295 1 1.007940 H 2.346458 2.449322 1.103029 1 1.007940 C1 1.307134 0.877664 0.186071 6 12.011000 O1 2.007450 1.631628 1.182543 8 15.999400 C 2.569593 1.040706 1.327857 6 12.011000 H1 1.710225 2.561139 1.054706 1 1.007940 H 3.500977 0.773070 0.785542 1 1.007940 H 2.580433 0.504636 2.295926 1 1.007940 H 2.425802 0.713660 2.629881 1 1.007940 H 0.714441 0.225449 2.526799 1 1.007940 H 1.738154 1.883766 1.738902 1 1.007940 H 2.558691 2.136998 1.488046 1 1.007940 H 3.112220 0.998838 0.991781 1 1.007940 H 0.097062 0.665875 2.331098 1 1.007940 H 0.069499 2.196290 1.397068 1 1.007940
This input ensures that the first atom of the reactant, C(1) in Figure 10, which is named C1 in the reactant structure definition for the saddle interpolation is aligned to the nineteenth carbon atom of the product, C(19) in Figure 10, which is also named C1, now, however, in the product structure. The same holds for the other numbered atoms in the above SADDLE input. Also note that the interpolation distance reduction is reduced to 2% by setting INT=2.0 in the SADDLE keyword line. This stabilizes further the saddle interpolation along the desired reaction coordinate. Of course, this reduction induces an increase in the number of saddlepoint interpolation steps and, thus, an increase in the computational effort. The MAX and TOL options can be used to change the maximum number of saddle interpolation steps and the tolerance for the interpolation convergence.