[Sorry about the previous misdirection.]

As I explained, the format for C40 (at least) should be Custom [hh]:mm:ss.

The specifier "[hh]" will display hours greater than 23.

But note that C40 displays 576:15:00 instead of 48:15:00, as you might expect.

That's because some of the "times" in C2:C39 exceed 24 hours.

So format C2:C39 as Custom [hh]:mm:ss as well.

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But really, I suspect the data in C2:C39 is not entirely correct.

For example, C2 8 days plus 8 hours (8:00:00). But B2 is simply 8 (hours?). So I suspect the 8 days is incorrect.

Similarly with C3. But C4 is correctly just 1 hour (1:00:00), and B4 is 1.

So I suspect the root cause of the problem is an inconsistency in converting column B (decimal hours) into column C (Excel time).

Enter the following formula into C2 and copy down through C39:

=B2/24

Again, format C2:C40 (even C41) as [hh]:mm:ss, even if hh:mm:ss should suffice. The format [hh] will permit you to have 24 or more hours in column B.