Single v Double

[Dimster]

I'm damn sure you guys have explained this once before so if anyone could point me to the thread I'd appreciate it. Can't seem to come up with the one I kind of remember that addressed this, it could be on the other site. Anyway here's the simply code

Dim a As Double
Dim b As Single
a = .12345678
Print a
b = Abs(a * 10000000)
Print a; b


So my search is to find out what happened to the 7 in the difference between variable a and variable b