So she has 10 holes and she had 4 lose lines and he plugged 1 and they divided in 2 making her max lvl increase by 1. This means she can like another 4 lvl max up. If he find a way to fill all 10 holes means 10 max lvl up?
Also you can't cut out line that are stuck to the bottom to delevel... if he could do that then Haruto would be invincible by cutting their enemies lines to make them lvl 1 (but vs majin seems not possible since they dont have lines).
Thinking part is now over... lets move on to the actual "plot"...
Damn Sarah
and is obvious with this that she is going to join the harem in the end of this arc.