What this score is
It is an in-app estimate produced by a language model that looks at sentence rhythm, phrasing predictability and vocabulary tells. It is not a Turnitin, GPTZero or Originality result.
Turnitin has no public API, so no tool can legitimately submit your work there on your behalf. Anyone promising a guaranteed 100% pass cannot verify that claim. Use this to make writing sound like you, then check with whatever detector your institution actually uses.