This is because your base unit of measure is NO.
Whatever information you enter in GI (or any other movement screen) any alternative unit of measure is ultimately converted to base unit of measure by system and this information is used to post the movement.
Since in your case the base unit of measure is NO, the conversion of 85 M is 0.0085 No.
Check transaction code CUNI, and under dimension 'No dimension' check unit of measure 'NO'. I would assume this will not have any decimal point rounding. See if you can change this to 4 decimal points, if you can this will solve your problem.
Regards,
Himanshu