Yep that hydraulic fluid is over filled. If you put 1 quart over what the manual lists as the capacity it is most certainly over filled. You will typically not be able to drain the fluid then put exactly the amount listed in the manual into the machine. I think the manuals list the capacity as a dry capacity Even after you drain oil there is still oil in there on the walls of the reservoir and such, and this will take away how much you can actually fill back with. If you overshot the manual by a full quart you are most certainly over filled. You will need to pop the drain plug and let it drain down some.
I will offer this, given i just did this same maintenance last week on my very similar L2501 - the level of the fluid will zip past that little glass gauge window very fast. Once you start to see the oil level at the very bottom of the glass, it takes very little after that point to shoot the level right past the glass. Im talking less than a quart and it will go from barely on the gauge to overshooting it. So you have to really watch that little window once you get a couple quarts in. Also make sure all your hydraulics are retracted. 3pt hitch is all the way down, loader arms are all curled up and down, so you dont have fluid sitting in the cylinders. Last thing I noticed that ill pass on is that it is SUPER important to be on level ground. Ive been surprised how just a very tiny incline or slight unlevel ground will make my gauge look empty sometimes. I had this happen just this weekend when out working.I was sitting on fairly flat ground, no inclines to the eye, and my gauge showed no fluid level at all. I thought wow im a little low now. I drove it back up to the garage and now it was back at halfway up the glass. Its very picky that little sight glass.