How much grease in drive-shaft zerk fittings?

[blackmax]

Just crawled under my truck yesterday to grease the drive shaft fittings. Some took just a pump or two before grease came squirting out of the seals....like normal. But there were 2 or 3 where I pumped maybe 20+ times.....and the grease just kept going somewhere??? Where was it going? Can you overfill.....probably not possible and just make a mess if you do, but I'm a little confused as to how much grease to put into the fittings where it doesn't become obvious that they are full. ??

 

[Gatafly]

When I first did mine it took 60 pumps until the slip joint moved. You want to keep .an eye on it while you are pumping and as soon as it expands you are done