Operator '-=' doesn't work as expected

[Machiavelique2]

int iNumber1
int iNumber2

Begin GameMode

	Let iNumber1 := iNumber2 := 10

	Let iNumber1 := iNumber1 - 0.27		; Return 9
	Let iNumber2 -= 0.27			; Return 9.73 (so the integer is now a float...)
End

This code has been tested with NVSE 6.3.5b and FalloutNV.esm only.