How does the benefit allowance refill?

I am currently on the disability leave portion of my maternity leave. I had 8 weeks for a c-section and given an 8 week extension for severe PPA (for a total of 16 weeks). I’m going to start my bonding leave next week and will return to work in Feb. I’ve used 16 weeks of my disability benefits and was wondering how that piggy bank gets refilled. If I go back to work and after a month or two cannot handle the transition- will my benefits refill for those 16 weeks I already used? How does this work? I’m very anxious about my return to work as my PPA is 100% sorted yet.