So I just got into fishing, loving it so far, all of my previous fishing rods have already had the line spooled onto the bell.  I bought a ugly stick gx2 today and some 10 lb test flourocarbon line to spool onto the spinning reel, and I thought I was doing it correctly (watched a few youtube videos explaining the technique) but when I went to do a practice cast out in the yard I flipped the bell up and pinched the line to begin my cast and about 9-10 inchs of line automatically spun off the reel? Thankfully it didn't get tangled but I would like to know what causes this?  Something I'm doing wrong? Is the line not spun tight enough around the bell?  Any help or tips would be greatly appreciated!  Thank you.

You have to spool fluorocarbon properly or it will get ruined. 10lb fluorocarbon is also way too thick for spinning reel. People use 6-8 lb, but you will run into trouble with those as well. I try to keep my spinning reel line that is not braid under 5 lb.

Honestly, you don't need fluoro, especially 10 lb on your spinning reel.  Take it off and get some 10 lb braid or 6 lb mono.   Go out and have fun, don't make it harder than it needs to be.

As said, 10# is too heavy for bass size spinning reels.  Next problem could be the spool is overfilled.

You didn't mention what size spinning reel you have. Both me and my fishing buddy have been using TD Advantage 2500A reels with 10lb Seaguar InvisX for the last 4 years with no handling issues at all. I have them on 4 of my rods, he has them on 2.

Don't know why guys are knocking the 10lb line on a spinning reel. 10lb is a good option for people that havn't mastered a bait caster and want to get the best bang for their buck. Also I'll throw a shad rap with 10lb on a spinning reel from time to time. When I finesse fish I'll have 6-8lb test line. You have to remember that 10lb invisx is pretty thin. 

without blaming the line, id also think of a couple of other things. perhaps you overspooled it/put too much line on it. when putting on line i try to leave an 1/8th inch of lip minimum around the spool(or as youre calling it, the "bell"). so maybe pull a few feet of line off and see if it still jumps off the spool. another thing to check for is line twist, if the line twisted while spooling it on, it may jump off as well...

10# fluoro is a bit much for a spinner.  I don't go over 6# on a 2500 series reel.