For example, a purchase of 100 euros will be shown on your statement as:
6 June 2016, 100 euros @ 1.284420 euros, £77.86 (meaning that 1.284420 euros= £1.00, so 100 euros divided by 1.284420 = £77.86)
100 euros @ the rate of exchange for the euro that is equivalent to £1.00, on the date your transaction was processed by Visa (e.g. 6 June 2016), which may be different from the date on which you made the transaction. See the FAQ: What is the "processing date" for my transaction above for more information.