Why are two classes with the same title showing different credit hours (not lab and lecture)?

So, I am registering all late about it…and I am confused. Math 170, for example, shows 7 courses and only one says 4.0 credit hours while the others say 0.0? I see no other differences that stand out. The same goes for Chem 122 where most classes show 0.0 but two say 5.0 (123 is the lab so I do not think it is because one is lab and one is lecture?). Any guidance? Their whole system is so different from my last school. The whole R for Thursday thing even made me think for a minute. Lol.