If you are making incremental progress in math, you are moving slowly but steadily forward. Incremental describes regular, measurable movements that are usually small.
Sometimes a basketball team might make a huge improvement, like a team that is 32-50 one year and then 50-32 the next. More often, progress is small and tiny — incremental. Anytime something is changing in any way, and the change is slow and steady, you can talk about incremental changes. A lot of life is like that. You might prefer to be making great or even miraculous progress, but incremental gains are better than none at all.