The phrase "a fair bit" is an idiomatic expression that means a significant amount or extent. It can be used to describe something that is large, considerable, or substantial in size, quantity, or degree. For example, one could say "I've been working on this project for a fair bit and I still have a long way to go." In this context, the speaker has been working on the project for an extended period of time and there is still much work left to be done.