(Much of this echoes what antlersoft says in their answer)
For a phone photo through the eyepiece that looks about right to me!
The size... the brightness... both are as I expect.
What you could try is to use the manual mode of your phone's camera and set the ISO down to minimum (100) and the shutter speed down to something like 1/60s.
Take a few shots, pick the best one, and make a zoomed+cropped version.
You should be able to see a point of white on the south pole and a hint of dark patches.
If the seeing's bad then you'll get awful results no matter what, so wait until the view is nice and crisp.
Now, when you look through the eyepiece, how does it look to your eyes?
Is it too bright? If so then keep watching the planet and your eyes will adjust and the contrast will improve.
Is it too blurry? If so then back off the magnification a bit until it's not blurry any more. A smaller crisp image is much better than a larger blurry image - your eyes will be able to pick out small details in a tiny image with time and practice.
Here's a lucky snap I got a few weeks ago:
And here's a zoomed and cropped version:
And here's one from one minute beforehand with automatic camera settings:
These were taken through the eyepiece of a 10" F/5 Dobsonian - very similar to yours. (I can't remember which eyepiece I had in at the time, I'm afraid! I think it was a 4.5mm but it could have been an 8.8mm with 3x Barlow lens, or even a zoom lens plus the 3x Barlow...all I do remember is that the seeing was exceptionally good that night and I was making the most of it!)
The good one was ISO 100 and an exposure time of 1/60s. The bad one was ISO 100 and an exposure time of 1/17s.
Hopefully these photos demonstrate that everything has to come together to be able to get a halfway decent photo: the seeing, the collimation, a steady hand, the camera settings... :-)