You know this has bugged me for awhile. The way a colon is used in maths is as a ratio.
So, 1:2 is 1 to 2.
2:5 is 2 to 5. This is the same as using the word "of", e.g.,
1 of 2, or 2 of 5.
So might it mean, literally,
5 OF 5? Could be a time expressed that way, as in
5 minutes till 5 o'clock. Or it could mean 5 out of 5. Just been thinking about this. Thanks