I've got a TI-84 Plus Silver Edition running 2.55MP (I think that's the OS? I'm sorry if it's not)

I'm not the best with all the terminology so I'm sorry if I get anything wrong. I'm not sure what I did to make this happen, but the little symbol in front of the Y1, Y2, etc is displaying what is shown in the photo. When I press enter to change that, it only has two other options, also displayed in the photo (I set it so the symbol in front of Y1 is what they all seem to have as the default, Y2 is the second option that I get when pressing enter, and Y3 is the third). It's supposed to be a diagonal line by default, and should have several options that don't look like any of those three, I know that much at least. 

I've used the graphing functions normally before, I'm not sure what's going on or how to fix it. I couldn't find anything in the user manual or in several tutorials, but then again I didn't really know what to look for, so I just looked in the sections about graphing functions, which yielded me nothing.

Thought I should ask for help here as soon as I can since I'm taking the SAT in a few days and will need to use this calculator.

Thank y'all for your help.

Sorry if this is a dumb question, how do I fix the graphing functions?