This is a doc explaining the standards for how to retime levels to conform with the shine-get timer (“SGT”, used for ILs) in various situations. Note that two ways in which IL timing deviates from (video-based) timing of longer categories are that it pauses during loads, and allows the Fast Text practice code, which saves time.
Evidence for rationale can be found here.
For a level done without SGT, this will give a retime, though it won’t account for loads or text.
Any level done without loadless SGT should be retimed in parts and summed, as explained here.
Cutscene Sublevel Retime
For a level done with SGT, this will give a retime of a final sublevel that loaded via an instantly-cancellable cutscene – notably all secrets.
This will adjust a raw retime (done from either video or timer) for any text done without the Fast Text practice code.