Every time I add a note, this happens. How do I reset it? It wasn't like this before. Thanks

Check which Input mode you are using. It appears you are using Insert mode. I don't use that mode, so I can't comment much more, but I understand that it increases the measure duration. (hence the + sign)

You have note entry set to insert mode. The note entry icon is am 8th note with a + next to it rather than a fancy N. Click the tringle to right right of it and select the correct input mode.