Seals are never guaranteed, but when in top 3, the odds are very high. highest at 1st, 2nd highest at 2nd, etc.

You either get a seal, or a consolation prize, i.e. a beastcoin.

It is also possible to get gather/craft accessory, but the % chance seems to be the same whether 1st provisioner or 20th provisioner. Extremely low.