vlookup with scroll bar not quite working

Use this in F4, copied down:

=$A$4+ROWS($F$4:F4)*$F$2*15/24/60

In addition there's something very strange about your vlookup. It is saying: Look up this thing. If the answer is zero, put N/A, otherwise look it up again.

Easier to use:

=IFERROR(VLOOKUP(F4,$A$4:$D$1769,2,FALSE),"N/A")

I's advise against using #N/A, as that has a specific meaning in Excel and is a useful diagnostic if/when things go wrong.