Reverse vs Timeless equip levelling

When I equipped both my reverse gloves and timeless staff at the same time I expected them to gain EXP equally, but based on HS's description (reverse gloves needing 70 EXP at level 1 compared to the timeless staff needing 80) I expected the staff to have less % than the gloves when I was done training. When I checked after training it turned out the staff was at 66% and the gloves were at 58%, which made no sense.

Is there a reason why my staff levelled marginally quicker than my gloves?