Odd subtraction behavior

[rolfk]

Your use of locals is necking you here badly. LabVIEW locals are (always?) read first in the context of a particular diagram part. So what happens when you enter into your sequence frame is that Synched Stamp Ticks and Stamp Ticks (and all the other locals) are read first, then LabVIEW starts to do the various calculations and front panel control updates such as updating the Synched Stamp Ticks terminal. However this is not something you should rely upon either. As far as LabVIEW is concerned, the evaluation of the local variable and the updating of its terminal when in the same diagram context is allowed to be in random order, and could even be done quasy parallel. It does mean that while LabVIEW has so far evaluated local (and global) reads before anything else in a particular diagram context, there is no rule, documented or not, that mandates that LabVIEW does this, and will keep doing this until LabVIEW 2030.

The correct way to program your diagram is to forget all the locals and wire them to the actual value in your diagram you want to evaluate.