Reddit NFT quantity limits seem deceiving to me as a first time buyer [SERIOUS]

Hi:

I didn't buy any Gen1 or Gen2 Avatars, but this time I decided to take a peak and for the first time in my life, I bought some NFTs (Gen 3 Avatars). I didn't buy them right when they dropped, but a day or 2 later I decided to take a peak and saw some I liked. I have three observations related to quantity:

1. As somebody buying for the first time, I find it a bit odd that they are advertised with a plus, like this one has 4500+. And this one has a quantity of 3500+. Since part of the fun and part of investing (for those who are doing this for investment purposes and not fun) is getting an NFT that has a low quantity, I find it odd as a first time buyer that it isn't just 4500 or 3500 (without the +).
2. Why do NFTS that have 2,500 say 2k on the front? Why not just put 2.5k?
3. Overminted NFTs. How does this happen? Is this done on purpose or not? After buying an Alicia Freeman NFT I liked, I checked out Stardust on OpenSea. I thought there were 150 only. But I'm seeing Stardust 226, Stardust 186, Stardust 232, and so on. This seems a bit deceiving to me. It feels like Reddit is selling something that is rare with only 150 to be minted and I assume some people bought them believing there would only ever be 150, but it looks like they were overminted by a lot. Then, I see others have been overminted too. Can somebody more experienced with NFTs explain this please. How do you know how many the + means?

Thanks.