Let’s calc!
How many blocks in a month? ~1440 (for a day) * 30 = ~43200
What is the total size of the generating balance now? = ~51M = ~51000k
So the chance for 1k Waves generating balance to find a single block for a month = 43200/51000 = ~85%
It means you can expect 0.85 blocks in a month with 1k Waves generating balance.