I had a formula made by @rockinfreakshow to fill background colour in cells depending on minutes added after a teacher's name but something happened and extra cell is coloured.

45 means 45 min so it should be only 2 cells coloured in green.

Here is the formula.

=index(let(Σ,xlookup(1,--regexmatch(B$2:B2," \d+$"),B$2:B2,,,-1),xmatch(cell("address",B2),address(row(Σ)+sequence(choosecols(split(Σ," "),-1)/15,1,0),column(Σ)))))