Weird evolution thing happening?

Syntax_st​ You need to look closely at the Defending upgrade on level 1 of the Fully Loaded evolution. It says your card can have +15 stats with a stats upgrade limit of 87. Heading accuracy is part of defending stats, so as many defending stats are gained on the card during this evolution, your heading accuracy will increase respectively.

For example,
1. A card with 89 defending will not gain any stats boost as it is already above the 87 max upgrade limit.
2. A card with 83 defending will gain only +4 on defending stats boost and will be stuck on 87.
3. A card with 67 defending will gain the full +15 on defending stats boost and will reach 82.

As much face stats for defending upgrades on each card, the respective proportional boost applies to in-game stats (i.e. head accuracy in your case).

Hope this helps. If you have any more questions, please feel free to ask. Someone from the community will be able to answer your questions.