Gem of Evasion Inquiry

not sure if the design is meant to be this way, Tier 1 gem of Evasion turns the player stat to 50% dodge for 15 sec. However, it does not add/stack to the players current Dodge rating/spells/buffs meaning if I have 30% it will simply cancel out my current 30% and cap it at 50%. Not sure if it will cancel out a player who reaches 60% dodge and when the Gem procs cancels out the 60% and switches it for 50%.