Most credit cards convert foreign currencies when the charge posts, so if the Rubel goes back up in the next few days, you will get charged more than the conversion rate you see now.
This is from Visa's website in regards to foreign exchange rates.
How accurate are the rates?
The rates you are shown are from Visa's internal database for foreign exchange rates and are updated daily. However, they are only meant to serve as an indication of the rate you could expect to receive from your issuing bank. As exchange rates change constantly, the rate is only accurate for one day. The exact rate you are charged depends on when the transaction is posted to the Visa system, which may be later than the day on which you paid, depending on how promptly each merchant handles their Visa transactions. Additionally, your final transaction amount may differ depending on whether the merchant converts the currency at the point of sale or if the bank that issues your card assesses a foreign transaction fee.