you have to add the 2% to all the other mana bonuses your hero may have if you hit a “mana breakpoint”, a hero will charge in 1 fewer tile (e.g., average heroes charge in 9 tiles instead of 10, at +12% mana generation - this is one of the most critical breakpoints as 9 tiles is easy to get from 3x3 matches)
remember that these mana bonuses can come from: troops, costumes, family bonuses, special skills/minion effects…
if you hit a “mana breakpoint”, a hero will charge in 1 fewer tile (e.g., average heroes charge in 9 tiles instead of 10, at +12% mana generation - this is one of the most critical breakpoints as 9 tiles is easy to get from 3x3 matches)