Decimal field not saving (precision 2, max size 18)

I have a decimal field with precision 2 and a max size of 18. Through some math, I got the number 2.45628549725315e^(-4) [calculation done by hand to check the math]

Shouldn't this number have been truncated at 2 decimal places, avoiding the max size issue altogether? The field is a financial multiplier which is why I used a decimal. Am I correct in my assumptions?

We're on Enterprise 7.5.0.1

Thanks!