Template:M summ GMRA 4

This provision says far less than its heft would suggest it does. In a nutshell:

• You can call for Margin if you have a Net Exposure, meaning the the amount the other party owes you — accounting for unpaid income and posted margin — is more than you owe it.
• As long as you meet eligibility criteria, it is up to the person having to post margin to decide what to post except that the requester can ask for any outstanding margin it has posted back. This scenario should only happen where the Net Exposure inverts between margin calls. But anyway: if you’ve posted away, you can ask for it back. Otherwise, the other guy decides.
• Where you post cash, you do so in the Base Currency and — stating the bleeding obvious here, as any fule kno — the transfer of cash creates indebtedness
• In lieu of Margin Transfers the parties can agree to “reprice” a Transaction — effectively restriking and settling it to market and creating a new Transaction in the same Purchased Securities at the prevailing rate — or to “adjust” it, in which case you can change up the Purchased Securities to something else altogether.

There follow some laborious provisions explaining exactly how this happens, but they do no more than badly codify common sense; in the real world your operations guys will figure it out and they definitely won’t be reading the Global Master Repurchase Agreement when they do.