My fault, there were two transactions, and I was mixing up the fees.

I went back and recalculated everything this morning using tools I have available here that I didn't have at home (like my brain). As far as I can tell the withdrawal was at the interbank rate, possibly with a day's delay. (The conversion amount comes out exactly if I use the following day's rate.) The additional charge was exactly 1% of the withdrawn amount in both cases.

With the ever increasing credit card fees, I'm going to return to using cash for more things, since using the ATM is a better deal at 1% instead of 4%.

I was also apparently incorrect about the fee not applying when using Citibank ATMs. This from their website:

If you use your ATM/Debit Card to get cash in the local currency at any ATM—Citibank or non-Citibank—then there is a foreign exchange fee that totals 1% of the transaction, in U.S. dollars. For example, if you withdrew 100 Euros at an ATM in Italy, and the value in USD was $125, then the 1% fee would be $1.25. This exchange fee is also applied when you use your ATM/Debit Card to make purchases overseas.