[If] one says to his agent: “Go and separate terumah,” [the agent] should separate terumah in accordance with the mindset of the homeowner. If he does not know the mindset of the homeowner, he should separate terumah using the intermediate [standard], one [part] in fifty. [If] he subtracted ten [parts] or added ten [parts], his terumah is terumah. [But] if he intention-ally added even one [part], his terumah is not terumah.