Use the first ticket to plan, not to guess forever
Enter the steer, drive, and trailer weights from the same scale ticket. CDLMath checks the axle and gross limits you enter, looks at the holes available on the rail, and recommends a whole-hole move. Forward means toward the tractor. That normally takes weight off the drives and adds it to the trailer tandems. Moving back does the opposite.
The starting position is counted from the frontmost usable locking-pin hole. If your rail ends before position 100, open the limits panel and enter its actual rearmost usable position. The result will stay inside that range.
The reweigh is the useful part
A pounds-per-hole preset is only a first estimate. Trailer geometry, hole spacing, suspension, fifth-wheel position, and freight placement all affect the transfer. The 250-pound and 400-pound choices are labeled as planning assumptions, not universal specifications.
After the first slide, leave the original ticket and starting position in place. Check I have the reweigh ticket, enter the new weights, the net holes moved, and the direction. CDLMath measures the transfer shown by those two tickets and bases the next move on the latest weights. It also rejects a reweigh when the direction is backwards, the gross changes too much, or the calculated position is outside the rail.
Example
The first ticket shows 12,000 steer, 36,000 drives, and 32,000 trailer at position 13. After six holes forward, the reweigh shows 12,000, 34,500, and 33,500. That move transferred about 250 pounds per hole. The current position is 7, and the next estimate is two more holes forward to position 5, putting the tandem groups near 34,000 each.
If both tandem groups already fit the entered limits, a slide may accomplish nothing useful. A trailer-tandem move also cannot remove gross weight or normally correct a steer-axle problem.