Credit score from one company increasing, decreasing by another?

Hello all, I apologize in advance if this is a stupid question. I currently have 3 forms of credit, 2 credit cards and an auto loan. My credit limit is around 6,000 dollars, and I utilize about 10-15% every month. Every month I check my updated FICO score from each of my credit card providers (Discover, Citi) and they differ by about 40 points typically.

This month my discover score went up 4 points to 742 while my Citi score fell by 6 points to 700. What’s the reason for this difference if they’re both FICO scores? Citi cites having too many lines of credit as a problem, while discover credits this as a benefactor to my score. For context, I am a 20 year old college student working full time, so I don’t have a long credit history (2 years). I’d like to raise my score as much as possible, thanks for any help