If you have models who don't count towards your bow limit, do they still count towards your total number of models for determining who else can have bows?

For example, I have 18 wood elves.

6 of them are rangers and do not count against the bow limit.

Of the remaining 12, can 6 have bows (1/3 of the total force), or can 4 have bows (1/3 of the total force discounting those who do not count towards the bow limit)?