Am I missing something on seeds?

Just returning to the game after quite a lay off and obviously Living Off The Land isn't a thing anymore... So, how exactly do you successfully farm?

I just harvested my crop from my painstakingly gathered seeds and if I take the seeds I get from harvesting and convert 100% of the harvested potatoes back into seeds I will have... the same number of seeds I started with and no potatoes.

I must be missing something, right?