normanstrong wrote ...
But the frame is 525 lines. That leaves 45 lines. Does
anyone know what each one of them does? I mean
specifically. Like, line x is the time of day, etc.

Most of them are not assigned to particular functions. Back
when RS-170 television was invented, the vertical interval
was required to allow the CRT beam to return to the other
end of the screen. Sometimes you can see diagonal lines
across the screen where the vertical interval is not blanked
completely.

Nowdays, they are used for vertical-interval timecode: VITC,
vertical-interval test signals: VITS (sometimes you can see
a single line of color bars, multi-burst, etc.), closed-caption
data (quite commonly seen as white dashes on line 21 changing
rapidly during dialog, etc.)

In the PAL territories, the vertical-interval is also used for
Teletext, etc.

Google for vertical-interval signals and you'll find more than
you wanted to know.