If I took two early withdrawals from my IRA in the last 60 days, can I rollover (repay) the first one, or only the last one?

I understand that the rule is that once per year you can take an early withdrawal from your IRA and if you repay (rollover) the funds within 60 days you will not have to pay taxes or a penalty on the withdrawal.

But my question is in the details.  If I took two early withdrawals within the last 60 days, can I:
* Only repay the last withdrawal?
* Repay the withdrawal of my choice, not necessarily the last one?
* Or are all of the withdrawals within 60 days treated like one big withdrawal even though it was taken in two withdrawals, and I could repay both?