Some ⚡ Actions may be Overflowable. This means that their ⚡ AP cost can be split between the current turn and your next turn.
Example
It is my turn, and I currently have 4 ⚡ AP. My buddy Bob is bleeding out next to me, and is asking me to use Medical Treatment on him. Medical Treatment costs 8 ⚡ AP, so I spend my 4 ⚡ AP now, and I will use 4 ⚡ AP next turn to complete the ⚡ Action.