Not sure but the 5213 for instance could be 5- the regiment , 2 - the company of the regiment, 1- the platoon of the company, 3- number of a tank in the platoon. Likewise the 7113 would follow the rule.
I don't think they are driving with the fenders up. Just the pic shows them during maintenace .
Back to the numbers...
I have found on one Polish forum info posted by a guy who served in the 25th Tank Regiment in Szczecin in 80'. According to him the numbers of the unit started with 52 ( 5201-5281). There were 5 companies , each consisted of 16 tanks.
The 1st Company, the CCO's tank number:5216
The 1st Platoon: numbers from 5201 to 5205
The 2nd Platoon: numbers 5206-5210
The 3rd Platoon: numbers 5211-5215
And the rest companies in the same way following the next numbers.
The Commanding Officer of the Regiment - a tank of the number 5281.
There are tanks with numbers 5201, 5202, 5207, 5213 and 5215 seen in the full image. So I would say the tanks could belong to the unit as well.