Oh yeah, learning the difference between mould temp and pot temp is a major step for a lot of people. Lee moulds are fine, the 1/2 ton pickup of the mould world. Easy to use for a lot of stuff if you know how to drive them, easy to abuse if you aren't paying attn. I will tell you right off the bat that a new Lee will often (always for me) need a couple of heating/cooling cycles before it acts right and gets with the program. I've always thought it was left over lube from the cutting process that caused this. Wash the thing out, even though yours is used, and let it warm on the edge of the pot. When you start pouring, fill the cavity and let a good amount of alloy pour over the sprue plate. I assume you'll start with a ladle. Hold the mould over the pot and let it run back into the pot. Let the alloy "freeze up" and give it a few more seconds before you open it. Don't make the mistake of standing there with and empty mould in your hand looking at what you just dropped. Keep filling and dumping and within a short time you should be getting pretty close to filled out, or well filled bullets. It's worth a look at the various "Leementing" articles out there that will fill you in on tuning a Lee mould. Thing to remember is that cool moulds don't make good bullets. Hot moulds do. When the mould reaches temp you'll find yourself having to slow a bit to let the casting cool enough to drop it without smearing the top or bending bullets as they drop. Yes, fresh cast bullets, especially longer ones bend, dent and otherwise get marred if they aren't quite cool enough when you drop them. You'll get a rhythm going eventually that allows you to pour, wait, drop, pour and the bullets start piling up. This is where the little 10lbs pots fail IMO. My pot holds an easy 30lbs and there have been times I've had to stop and add alloy. Feeding a 10 cav H+G can be too much of a good thing sometimes! The little 10lbs pots empty real quick.
Well, I see I'm prattling on again. Anyway, just be aware the mould temp is not pot temp and that you don't fix fill out, usually, with pot temp, but by casting faster.