Time Calculation

Object - to determine the time lapse (in hrs/mm) between a given set of times.

Cell M - start time. I use a drop down menu to generate this value - it is in 15 minute increments as is formatted h:mm

Cell N - lunch start. I use a drop down menu to generate this value - it is in 15 minute increments as is formatted h:mm

Cell O - lunch end. I use a drop down menu to generate this value - it is in 15 minute increments as is formatted h:mm

Cell P - finish time. I use a drop down menu to generate this value - it is in 15 minute increments as is formatted h:mm

Cell R- hours worked =((P7-M7+(P7<M7))-(O7-N7+(O7<N7)))*24
format - general

This formula returns the correct result (hours worked) for some values and appears to add 24 hours for others. When I override the list function and manually input the times in cells M, N, O and P it always returns the correct result. I have checked the format of the list drop down times and they appear to be all uniform so I am puzzled at to why I get a different result between a manual input and using the list.

Any help appreciated.

Pls find attached.SAMPLE.xlsx

Thank you that formula appears to work.

Am still puzzled as to why the calculation works with manual input.