They lost a lot at the beginning. Now they are left with what they can produce new and refurbish from storage.

I've seen estimates of this being 300 to 2000 tanks annually (1 to 6 tanks daily). Since they are in a big push right now they are likely using up their operational reserves that they built up over months.

So they can afford to lose more tanks than they "produce" daily, but how long they can keep up this attrition rate up is unclear. I've seen estimates that they have 3000ish tanks left in field/reserve/storage.

However, it's unclear what condition these stored tanks are in. They likely used the newer tanks and those needing the least refurbishment first, leaving the only the dregs (old and heavily damaged) left.

Edit: added a couple clarifying words.