John wrote...
I have the following Index formula which is not producing the correct result
and I am unsure of why

{=INDEX(StartTime_HoursWorked,MATCH(1,
(Date_HoursWorked=H$9)*(StaffNo_HoursWorked=$B$13 )))}
....

The problem is that you're looking for the first exact match, so you
need to include the 3rd argument to MATCH, and that argument needs to
be zero or FALSE.

=INDEX(StartTime_HoursWorked,MATCH(1,
(Date_HoursWorked=H$9)*(StaffNo_HoursWorked=$B$13) ,0))