425 trans oil

ok had a senior moment a few weeks ago and just realized it today. when attaching the quick connections hose and freeing the selector valve for my 425 i lost a bit of fluid in the process. so i topped it off with 20w-50, the oil that was meant for my Ferris Zero Turn hydro's! Now I know that it needs J20D and the thing just had a trans oil change and filter. I put maybe 1/8-1/4 quart of the 20w-50 in and have run it a few times since. Question is should I dump the oil and put fresh oil and filter on? the manual specifically states do not mix oils but would like to hear it from someone with experience with these hydro's if that amount of oil will effect anything. Thanks