Integer math using floats

Doing some tests, I see that Floyd appears to be correct.
This code succeeds:

For biter = 1 To 100
  For iter = 1 To 16000000
  	a# = a# + 1.0
  Next
  For iter = 2 To 16000000
  	a# = a# - 1.0
  Next
Next
Print a#
WaitKey()
End

and returns the result 100.0

This code fails:

For iter = 1 To 17000000
	a# = a# + 1.0
Next
Print a#
WaitKey()
End

and returns the result 16777200.0