On Sheet13, paste each of these lines into C2 through O2, but make sure to press Ctrl+Shift+Enter rather than just Enter. Then you can fill down with that formula.
=SUM(IF(IFERROR(FIND(A2,Sheet1!B$4:O$33),0),IFERROR(1*MID(Sheet1!B$4:O$33,LEN(A2)+2,LEN(Sheet1!B$4:O$33)-LEN(a2)-2),IF(Sheet1!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet2!B$4:O$33),0),IFERROR(1*MID(Sheet2!B$4:O$33,LEN(A2)+2,LEN(Sheet2!B$4:O$33)-LEN(a2)-2),IF(Sheet2!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet3!B$4:O$33),0),IFERROR(1*MID(Sheet3!B$4:O$33,LEN(A2)+2,LEN(Sheet3!B$4:O$33)-LEN(a2)-2),IF(Sheet3!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet4!B$4:O$33),0),IFERROR(1*MID(Sheet4!B$4:O$33,LEN(A2)+2,LEN(Sheet4!B$4:O$33)-LEN(a2)-2),IF(Sheet4!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet5!B$4:O$33),0),IFERROR(1*MID(Sheet5!B$4:O$33,LEN(A2)+2,LEN(Sheet5!B$4:O$33)-LEN(a2)-2),IF(Sheet5!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet6!B$4:O$33),0),IFERROR(1*MID(Sheet6!B$4:O$33,LEN(A2)+2,LEN(Sheet6!B$4:O$33)-LEN(a2)-2),IF(Sheet6!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet7!B$4:O$33),0),IFERROR(1*MID(Sheet7!B$4:O$33,LEN(A2)+2,LEN(Sheet7!B$4:O$33)-LEN(a2)-2),IF(Sheet7!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet8!B$4:O$33),0),IFERROR(1*MID(Sheet8!B$4:O$33,LEN(A2)+2,LEN(Sheet8!B$4:O$33)-LEN(a2)-2),IF(Sheet8!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet9!B$4:O$33),0),IFERROR(1*MID(Sheet9!B$4:O$33,LEN(A2)+2,LEN(Sheet9!B$4:O$33)-LEN(a2)-2),IF(Sheet9!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet10!B$4:O$33),0),IFERROR(1*MID(Sheet10!B$4:O$33,LEN(A2)+2,LEN(Sheet10!B$4:O$33)-LEN(a2)-2),IF(Sheet10!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet11!B$4:O$33),0),IFERROR(1*MID(Sheet11!B$4:O$33,LEN(A2)+2,LEN(Sheet11!B$4:O$33)-LEN(a2)-2),IF(Sheet11!B$4:O$33=A2,8,0)),0))
=SUM(IF(IFERROR(FIND(A2,Sheet12!B$4:O$33),0),IFERROR(1*MID(Sheet12!B$4:O$33,LEN(A2)+2,LEN(Sheet12!B$4:O$33)-LEN(a2)-2),IF(Sheet12!B$4:O$33=A2,8,0)),0))
=B2-SUM(C2:N2)
Some assumptions:
- Sheet 13's row 1 is used for header names like name, starting, remaining.
- Your first 12 sheets are called Sheet1 through Sheet12.
- All the sheets look roughly like your scan, i.e., the area we want to search for names is B4:O33 on any given sheet.
- There are no typos in people's names.
This will make a monthly total, and then a grand total in the O column.