my maths would be .....

you need one of the 4 Js or one of the 4 Ts out of the 47 unseen cards THEN you need the "other" that didn't come on the turn, i.e. EITHER the 4 T's OR the 4 J's so....

8/47 * 4/46 = 1.4%

and, yes, this may be even lower if the T and the J that come are of the same suit.

however, I wouldn't necessarily need to know this because I would almost certainly just fold!