That reel is rated for 10 to 14 lb. line and would probably take well over 300 yards to spool it all full with 6 lb.
If it was me, I'd get the cheapest 14-17 lb line I could find and spool that on until it was a bout 3/8" short of being full on the spool.
Then, I would tie a blood knot and finish topping it off with some decent quality 6 lb. Personally, I like the Vicious 6 lb Hi Viz panfish line - it has very low memory and behaves the best of any mono I've ever used. When you break off enough that you're losing casting distance or the line is getting frayed and ratty, peel off the rest of the 6 lb and fill it back up with fresh line. A 1/4 lb spool of Vicious 6 lb has 2360 yds. for $6.99 from the factory web site so that would let you put on fresh line about as often as you wanted. Vicious 6 lb Hi Viz Yellow.
The The Abu Garcia web page lists the following capacities in yds. for different line weights for your SX40.
210/10 180/12 150/14
Have fun with it
Crappie and Bluegill are my top two favorite fish to go after. Nothing to me is as much fun as catching a bunch of big ole bull bluegill when they are stacked up on beds. Tasty too!!
And Welcome to the forum!!!