You are very welcome Mary.
I fill hundreds of markers about every other month (for classes) and I STILL over fill some of them... LOL
It won't harm your marker, it just wastes ink.
If you do overfill (it starts to drip out the brush tip) then put the chisel tip back in, let it sit for a bit and then if it still is drippy, scribble a bit on some scratch paper until it stops dripping. I also like to put the cap back on the chisel end first and watch the brush tip. Sometimes if it is just about too full the pressure of putting the cap on will squirt some out the brush end.
If you put the caps on when a marker is overfilled, you might end up with a cap that sticks tight or ink that drips out when you pull the cap off. (Ask me how I know! LOL)
Have fun with your markers!!!