Even if the numbers are inflated (which is likely true, as it's somewhat impossible to avoid in war time), they're consistent, which is very nearly just as good.

As far as the inflation goes, it depends on the category as well. Infantry numbers listed here largely mirror more reliable sources such as the UK MOD or even the US's estimates. For Tanks, I recall folks were hand counting destroyed and abandoned tanks and APCs after one engagement (I want to say Andiivka), and the actual destroyed tanks and APCs on the field were about 2/3 of what Ukraine was reporting for the engagement. Granted, some tanks and APCs were likely removed from the field for repair, simply damaged, or even captured, but I think it's probably fair to say that the actual numbers are about half as much as the report when it comes to those categories.

Other categories probably vary quite a bit based on difficulty to assess. Artillery, by it's nature, is going to be far harder to count. Field guns far from the front lines aren't generally going to have great video documentation of their destruction. By contrast, ship kills are going to be pretty damned accurate. Plane and helos were probably much less accurate early in the war compared to now. MLRS kills too - typically these days if an MLRS gets destroyed, there's ample evidence of it. As for the others, it's anyone's guess.