I recently bought an used ball with Grip-Lock  pitches for the inner and outer sleeve is 1/4 but the slug is 3/16 what pitch am I really feeling.

Gotta wrap my head around this . . so you're saying the hole in the ball itself is 1/4 reverse, and the pitch in the slug is an additional 3/16?  That would total 7/16.  Or are you saying that the ball itself is 1/4 reverse, but with the slug installed, it reads 3/16?  With the slug installed, whatever pitch the gauge says is what you're feeling.  But like itsallaboutme said, it's REALLY hard to tell the difference when there's only 1/16 difference.  I'm a little unclear on what you're saying though, but either way it sounds like a screw up or a patch job by whoever drilled it.  You drill the hole in the ball at the target pitch, and the slug at 0.  Slug should always stay at 0.  If you change pitch, you plug and redrill the hole in the ball, not drill a new slug. 

Oh, ok.  So the drill bit came out the side of the slug a little towards the bottom?  I'd say that it's closer to 5/16 or 3/8 depending on your thumb size, I've drilled 1/4 reverse in a 1 1/4 slug before with a decent sized bit with an oval and not punched through the side, but either way, I'd just plug the thumbhole and start over.  Not being able to lock down what the pitch is isn't good in the first place, and it sounds like too much reverse anyway.