Excel when dealing with DateTime values, will not accept negative values.

From the looks of it, Google sheet has logic built in to wrap negative time into previous 24 hour cycle.

What you can do is add date portion to time value to avoid negative time value. Or when the calculation results in negative value, add 1 (i.e. 24 hours) to time value.

=IF(C9="","",IF((C9-'Schedule 16 Oct'!$B$13)<0,C9+1-'Schedule 16 Oct'!$B$13,C9-'Schedule 16 Oct'!$B$13))