There's a good chance the low number is due to some vet stress. Oddly enough, some cats' numbers drop from stress. Next time, get a test before you leave so you'll have a way to know if this is the case.
The 38 is an automatic dose reduction, which is exactly what you did for PMPS to day. You should shoot 0.75u tomorrow AM. The worst that can happen is that the reduction doesn't stick and you raise the dose.
If you want to see an alternative to putting numbers in the comments section, see Gabby's SS. You will need to manually change the colors when you put more #s into the SS.