I can't imagine you are doing anything wrong. Perhaps different CAT scales have different setups. The one we visited recently, in northern New Mexico, had four weighing pads, all of which weighed simultaneously. The pads were short enough that the three axles of our Explorer and TM could have spanned any three of them.
You could make two weighings, of course, and ask nicely if they would charge you for only one. For example, pull forward until the front axle of the tow vehicle on the second pad in line, and the rear axle of the tow vehicle and the TM axle are on the first pad. Record these two weights. Then pull forward until both axles of the tow vehicle are on the second pad, and the TM axle is on the first pad. A little subtraction, and Bingo!
If they insist on charging you twice, I guess that the extra nine bucks is annoying, but probably worth it.
Bill
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