* Only repay the last withdrawal? That is allowed.
* Repay the withdrawal of my choice, not necessarily the last one? That is your choice to make.
* 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? Each withdrawal is it's own situation ... sorry. The new rule was to limit tax free 60 day loans to ONE per a 365 day period.
Presumably these are distributions from one or more traditional IRAs. You are only permitted to roll over some or all of one of these distributions back to a traditional IRA and the choice of which one to roll over back into a traditional IRA is yours to make.
However, Roth conversions are not subject to the one-per-365-days rollover limitation. You have the option within 60 days of the distribution to deposit some or all of the either or both of these distributions into a Roth IRA explicitly as a Roth conversion (not as a regular Roth IRA contribution). If you do so, you'll still owe taxes on the conversion but will not own any early-distribution penalty.
Also, rollovers from a traditional IRA to a qualified retirement plan like a 401(k) are not subject to the limitation. If you have a 401(k) or similar plan at your employer and the plan will accept before the expiration of the 60-day deadline an indirect rollover of money from the traditional IRA, that's another possibility to avoid both tax and early-distribution penalty.