Kitchen Pantry Shelves
Meas Width Out-Of-Sqr Meas Net Width Shims
Nbr Height Front Back FL BL FR BR FrontBack FL   BL   FR   BR  
1 82-1/4 15-1/16 15-3/16 5/16     0     0     9/16     14-3/4 14-5/8 9/16 3/16 1/4 3/4
2 68-3/4 15 15-3/16 5/16 0 0 11/16 14-11/16 14-1/2 17/321/87/3213/16
3 55-1/4 14-15/16 15-1/8 5/16 1/16 0 9/16 14-9/16 14-9/16 15/32 5/32 7/3223/32
4 41-3/4 14-15/16 15-1/8 0 3/16 0 3/16 14-3/4 14-13/16 1/4 11/32 7/1617/32
5 28-1/4 14-7/8 15-1/16 0 5/16 0 0 14-9/16 15-1/16 5/32 13/32 15/3213/32
6 14-3/4 14-3/4 15 0 1/2 1/8 1/16 14-5/8 14-7/16 3/16 19/32 5/165/32
7 1-1/4 14-5/8 15 0 3/4 0 0 14-5/8 14-1/4 3/16 3/4 3/160
Shim Calculator

From the table above the narrowest Net Opening Width is 14-1/4", so all shims will be based on a 13-1/4" wide drawer.   I subtract the front out-of-square measurements from the front width measurement to get the net front width, same for the back.   Then cut shims to center the drawer in the remaining space minus 1" for the total slide thickness.  
The pantry closet is wider at the back than the front in most measurements.  

Square measurement with 3/8" face shim on right side to match side walls.
V Spacing is 13-1/2"

FL = Left Front     BL = Left Back     FR = Right Front     BR = Right Back