Question about Pot Output (The math aint mathing)

So I'm relatively new to the game, but having a blast testing out different operations and strategies. But something is driving my crazy and I need either validation that I'm not terrible at math or someone to correct me. If this is a common or well known issue, please feel free to downvote me to oblivion...

In the storage unit, I've got a cozy little weed operation, growing each strain on a cycle. I've got 5 pots (full spectrum lights, fertilizer and 3x Soil) and a botanist to keep it rolling while I do mixing and packaging. Should be easy to plan this right?

12 bud per plant X 5 pots = 60 total. So I need 60 baggies, 60 of whatever mixer. and so on.

I keep getting weird numbers. 72 once, 64 a few times, and I just got 68. I have no idea what's going on, but it's driving me nuts. I'd forfeit the extra product just to have the production run smoothly.

Any ideas? Bonus points if you can tell me whether or not drying racks are worth it for the next iteration.