I've been searching and can't find a source to explain the extra tokens in the weekly cache. Is it one extra token for each M+ completed above 10? Do they provide more AP the higher the M+ you've completed?
I believe they give you a higher tier of base token at 15 again, and then resume adding small tokens on top. Its basically done this way because they didn't want to create a new higher base token for every single level, so instead they give you partial tokens.