No limit on seeds... You do not have to be authorized to cultivate to posses but you can not have plants.
If you are Prop 203 cardholder - (Authorized or Not Authorized)
"Medical use" means the acquisition, possession, cultivation, manufacture, use, administration, delivery, transfer or transportation of marijuana or paraphernalia relating to the administration of marijuana to treat or alleviate a registered qualifying patient's debilitating medical condition or symptoms associated with the patient's debilitating medical condition.
"Marijuana" means all parts of any plant of the genus cannabis whether growing or not, and the seeds of such plant.
What you may posses - (presumption of medical use)
"Usable marijuana" means the dried flowers of the marijuana plant, and any mixture or preparation thereof, but does not include the seeds, stalks and roots of the plant and does not include the weight of any non-marijuana ingredients combined with marijuana and prepared for consumption as food or drink.
Your limit which satisfies the presumption -
"Allowable amount of marijuana" (i) Two-and-one-half ounces of usable marijuana; and
(ii) If the qualifying patient's registry identification card states that the qualifying patient is authorized to cultivate marijuana, twelve marijuana plants contained in an enclosed, locked facility except that the plants are not required to be in an enclosed, locked facility if the plants are being transported because the qualifying patient is moving.
Just from the definitions it explains your question... Seeds are not counted as plants and seeds are not counted towards your allowable amount. Same goes for "stalks and roots of the plant"...