A surgeon and two assistants perform an operation.
A surgeon and some assistants perform an operation.
Sentence 1 states two assistants whilst sentence 2 states some assistants.  Sentence 1 is more precise as it tells us exactly how many assistants.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_perform(e1) & n_operation(x3) & n_assistant(x1) & card_eq_2(x1) & of(x1,x2) & n_surgeon(x2))
exists e1 x1 x2 x3 x4.(Theme(e1,x4) & Actor(e1,x1) & v_perform(e1) & n_operation(x4) & subset_of(x3,x1) & n_assistant(x3) & subset_of(x2,x1) & n_surgeon(x2))