How to set my payment terms when the amount client set isn't relevant to the project?

[andrewcassmedia]

Hi everyone, so I went to go submit my very first proposal on Upwork. The client listed the job as a "fixed price" paying $200, but in the description they clarify that they don't know what the going rate for video editing is for an ongoing series of weekly YouTube videos, and say they're happy to work that out at a later stage of the process. So it's clear to me that they didn't know how to properly label their project (I understand, being new to Upwork myself and still figuring everything out). I imagine we'll negotiate a different per-video rate. But submitting my proposal requires me to specify how I'd like to be paid. Should I just say "by project" even though one sum of $200 doesn't make sense for an ongoing weekly video job, or "by milestone" and just put in some made-up ways to divide the $200? Thanks so much!