0 seed plants produce approximately 0 Carrot seeds. You need 64 more for the 64 crop positions next cycle. Seed plants need 0 Carrot from an earlier harvest to start.
This is a flat, obstacle-free grid estimate. Growth radius is an obstacle check, not an exact planting-distance rule. Walls, uneven ground, trees, sky access, and nearby plants can change what grows. Harvest estimates exclude random farming-skill bonuses and round the total down. Vines need a different layout and are excluded.