@drimplausible @lynnesbian Axle Counters are not about reporting the length. They are about "The same number of axles and thus cars that went in on the beginning of the block left it at the end of the block". (Or even, on either side, in case of reversing / split trains). Which is equivalent to what we're interested in, namely, "There are no cars left in the block, and we can leave the next train in at full speed".
So as long as the counter doesn't remain at 0 when the full train is in, an overflow isn't much of a problem. (Bad edge case: The train stops after exactly 256 axles have been counted in)