Uses of MAX - ongoing problem needs help!

Hello All,

I'm having difficulty with an ongoing issue using a MAX formulas. On the attached spreadsheet, on page 'Matrix' I have a sumif formula that is looking at sheet '1 - RV53B' column B11:D18.

I've highlighted row 4 in '1- RV53B'. This job starts on one date and finishes on another, but to do that it runs over 2 different shifts a day. Because my MAX formula in column C11:D18 is looking at columns L (Morning) and M (Afternoon) it isn't taking into account if a job starts in shift 1 on the first day and ends on shift 2 on the second.

I've written an example of how it should be!

But I can't get it to work within a formula!

Any ideas how I can sort this?