Ability Boosts

At 5th level and every 5 levels thereafter, boost four different ability scores. You can use these boosts to increase ability scores above 18. Boosting an ability score increases it by 1 if it's already 18 or above, or by 2 if it starts out below 18.

Your eidolon also gets four ability boosts at these levels. The eidolon's ability boosts follow the same rules as yours.