this is what happens when secretaries* use excel.
using a colon in a cell turns it into a timevalue. The numerical value in the excel database attributed to something with a : is of no use to you.
Use text handling functions (such as LEFT, RIGHT, LEN and FIND) to strip that ratio expression into it’s two components (divisor, dividend) then you can do your maths. If 1 is always your dividend, then that makes it faster.
* could be male, could be female. Definitely shouldnt be allowed near Excel
And that’s what happens when you don’t know how to use the text to columns with : as the delimiter 😉