odd maximum ability scores

the monk and barbarian have at level 20 two stats scores increase by 4, to a maximum of 25.
I don't understand why the maximum is 25 if both 24 & 25 give a +7.
Does it stack with something that increases the max score with +1 to make it max 26?

You can also get more epic boons if you continue past level 20.

Quote from Jurmondur >>

You can also get more epic boons if you continue past level 20.

 This is exactly why. As you gain more epic boons, you can increase your ability scores to a maximum of 30, so the 25 means you only need one more epic boon to hit that next ability modifier increase.

Quote from Sirius_Lazaurs >>

the monk and barbarian have at level 20 two stats scores increase by 4, to a maximum of 25.
I don't understand why the maximum is 25 if both 24 & 25 give a +7.
Does it stack with something that increases the max score with +1 to make it max 26?

 Additionally, tiebreakers go to higher scores… tiebreaker between 24 and 25 goes to the 25 on a same dice roll.