There are a few threads on this already if you search for them. Here's one http://www.badmintoncentral.com/forums/showthread.php?t=78445
I know 285 would be the measurement from the bottom of the handle but is that head heavy, balanced or head light? and what does ± 5mm mean?
I'd consider 285 balanced myself... 290 and above would be head heavy to me. The ± 5mm is the tolerance, so 285mm ± 5mm would mean the balance point would be anywhere from 280mm to 290mm.