i know i have the same problem. i got 2 pips then i get a power pip and it screws me up because for some reason it wont let me use my 4 pip spell.its really annoying when you really need the card and you die because of this problem. i dont know if they did that on purpose or its a bug.
hey at first i didnt understand it either.but then i found out that you can only use power pips in you school. ok lets say this you have a helephant and stormzilla and your primary school is fire(like me).then you have 4 pip and a power pip that ecuals 6 pips but for storm school as your secondary that would equal 5 becuse it's like having a normal pip.so having a power pip only goes with your primary school. hope this helps you