Excel function for hh:mm

Formula:

=G2*24*60

and copy down

PS. of course you can write

=G2*1440

but then you don't see why it works

other concept:
write in empty cell 1440
Ctrl+C
select all your green column,
Show Paste special dialog
check Multiple
Paste
(dont unselect) Format all cells in green column (still selected) as General