adding a product weight is different in 3.x?

Hello in mp 2.x I was able to add a product that was 0.4 or .25 of an oz 1/4 of an ounce. when i add a 0.24 it gives me errors. how do we add the proper ounce in? Basically it's a DvD and on my scale says 0 lbs 0.4 oz