The "inverse" of a currency pair is not always equal to the exchange rate of the opposite pair because we receive spot rates directly from contributors and market makers for each currency pair. 

For example: USDEUR has a value of 1.3050. The inverse of this rate is 1 / 1.3050 = 0.7763. You may expect that the exchange rate of EURUSD should equal 0.7763 at the same time. While the two numbers should be very close, there is no guarantee they will match exactly, as the spot rate of EURUSD comes directly from market makers and are not calculated on our end through the inverse of USDEUR.