I've bought vape cartridges several times here. The last one I bought was only filled 80-70% with oil. Which is odd. I thought it might be light, but I don't know. I was told that sometimes the oil seeps up inside. Any ideas They said

Yeah sometimes that does happen and you'll notice it immediately will because it'll feel like it's clogged when you try to hit it. The other thing is is not all cartridges are the same. Some cartridges are longer and have larger tubes inside some are smaller have smaller tubes inside it all depends on the supplier. A 1/2 Oz cartridge will look like there's less due to the length of cartridge. Considering how regulated the suppliers are in RI I'm sure they are legit.

The wick inside the vape also holds oil that is soaked into it