"Tolken förstår troligtvis vad han säger."

How about "likely" in place of "probably"?

I find this ambiguous. Does it mean:

1.) Does the interpreter understand what he (himself) is saying?, or

2.) Does the interpreter understand what he (someone else) is saying?

In English we might say, "Do you think he understands what he's saying?" meaning, does the speaker understand the gravity of what he (himself) is saying? Or, is the speaker babbling on without actual knowledge?"

Is "troligtvis" related to the verb "tro"?

Is "The interpreter apparently understands what he is saying" really wrong? Doesn't troligtvis mean "we believe it is so", "it seems so"?