Medals on straps

Okay not sure if this is mentioned elsewhere but been unable to find it

My question had to do with medal boosts and how they are applied and if this is an error that needs reporting back

Put a level 4 medal on that has a gem damage +315

Yet when I look my red damage is not even over 100 when the rest are.

I know when you have gem defence on its put together on the other side but nothing for all gem damage

Any help would with this would be great

TIA