Manually it's easy, because the base and pack size is always the first information in the cell and the pigment information follows after. Also, all pack sizes are appended with "L" (i.e. litres), whereas pigment numbers are just numbers.

So you could never get e.g. G:10 M:20 M:2.5L, it would always appear as M:2.5L G:10 M:20 in the recipe cell.