Ok, so as I was leveling, I was told 9 gapping was based on the numbers on the bottom right hand corner of the Skills tab.

I believe it says like Mastery Total 17/28...But then I heard it was your level minus your highest mastery level (IE. Wizard Mastery Tree)
So if this is true, have I been leveling with a 0 gap. I'm lvl13 with Wizard Mastery lvl13.
Should I start over, or should I just begin gapping right now?
Is it OK if I 5 gap, instead of 9 gap?
I'm a wiz/cleric.
Thank you all for the help.