I don't know why I didn't see this before, but I can just use the right() function. So if I want 1 decimal place and 4 whole digits (with the decimal point), I can do the following, which will convert 12345.67 to 2345.7
right(
numberFormat(
{tag}, "0.0"),
6)
This will make it a string, which is fine for displaying. But if I needed it as a number for some reason, I could put all that inside the toFloat() function.