I can't see that image - however if you are open to using helper columns then I have a solution for this (hopefully!!)
To simplify the issue of whether the time/date is within mon-fri 8:30-17:00 setup a helper column for each of the columns currently (so you have 4 columns initially, make 4 more - i'd suggest adding a prefix such as "Imp. "
So if A1:D1 currently are your headers, make E1:H1 the Imp. headers
With the data stored in 2nd row (A2:D2) use the following formulae for E2:H2
E2:
=IF(TEXT(A2,"ddd")="Sat",A2+2,IF(TEXT(A2,"ddd")="Sun",A2+1,A2))
F2:
=IF(E2>A2,8.5/24,IF(B2<8.5/24,8.5/24,IF(B2>17/24,17/24,B2)))
G2:
=IF(TEXT(C2,"ddd")="Sat",C2+2,IF(TEXT(C2,"ddd")="Sun",C2+1,C2))
H2:
=IF(G2>C2,8.5/24,IF(D2<8.5/24,8.5/24,IF(D2>17/24,17/24,D2)))
Finally the Working Hours (Column I) cell I2:
=(NETWORKDAYS.INTL(G2,E2,1)-1)*8.5+(F2-H2)*24
Format as a number.
| A | B | C | D | E | F | G | H | I |
1 | Completed Date | Completed Time | Report Date | Report Time | Imp. Comp Date | Imp. Comp Time | Imp. Report Date | Imp. Report Time | Working Hours |
2 | 05/05/2019 | 12:07:06 | 02/05/2019 | 11:25:27 | 06/05/2019 | 08:30:00 | 02/05/2019 | 11:25:27 | 14.08 |
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This shows the table in an example (random data entered for A2:D2 - the working hours should be correct though).