Latest report is Manafort's agreement was only about non campaign issues. The caveat is of course he probably has to answer ALL questions on ALL issues including the campaign.
Goes to my previous comment all is not as it appears.
I suspect SP Mueller has a list of all the bullet points worth investigating. Manafort can only provide details of the ephemeral threads which may connect these items i.e. details of Russian meeting, which may corroborate previous testimony from Trump's and Kushner, or refutation of Russian denials. I don't think he can provide any "new" avenues of investigation.