Two girls are sitting at a table with a green marker standing up right on the table between them.
Two girls are at the table.
Both sentences tell us that there are two girls. If two girls are sitting at a table then it is already known that they are at the table.
exists e1 e2 s1 s2 x1 x2 x3 x4.(with(e1,x3) & between(e2,x1) & n_thing(x1) & r_right(e2) & on(e2,x2) & n_table(x2) & n_table(x2) & a_up(s2) & Manner(e2,s2) & Actor(e2,x4) & v_stand(e2) & (x3 = x4) & n_marker(x3) & a_green(s1) & Theme(s1,x3) & at(e1,x2) & Actor(e1,x1) & v_sit(e1) & n_girl(x1) & card_eq_2(x1))
exists p1 x1 x2.(n_table(x2) & at(x1,x2) & n_girl(x1) & card_eq_2(x1))