The win percentage is currently calculated as wins / (wins + losses + draws). I checked your current Ascent lifetime stats and you have 57 wins, 49 losses, 5 draws, and 111 matches played in total right now.
As you can see, your win percentage is 100 * 57 / 111 = 51% which is what our website currently shows. Basically, you need just a few draws to lower your win percentage. If you get 100 draws in a row, your win percentage will be 27%.