How do I assign episode number to multiple episodes before S1.E1?

I am currently trying to add two episode titles to a web series currently already listed on IMDb. But the two episodes, titled episode zero and episode 0.5, aired before the first episode of season one, which has the episode number of 1.1, and that leaves only the episode number 1.0 for the two episodes I'm trying to add. But IMDb doesn't seem to allow for multiple episodes under one number. It would be even more confusing if I assigned 1.0 and 1.1 to the first two episodes because then the actual S1.E1 (deemed on the show's website) would show as S1.E2 on IMDb. Does Anyone has experience dealing with such situations? Any advice and help would be greatly appreciated.