One who increases the terumah portion, R' Eliezer says: [It is effective up to] one-tenth, like terumas maaser; [if he designated] more than this, he makes it terumas maaser for another place. R' Yishmael says: [It is effective up to] half chullin and half te-rumah. R' Tarfon and R' Akiva say: [It is effective] as long he leaves some chullin there.