In his WC testimony, Junior Jarman is adamant that when he and Hank Norman enter the TSBD through the Houston Street dock entrance to go up to the fifth floor, they have to go around to the west elevator as the east one is on the sixth floor. Something he confirms once they get up to the fifth:
Representative FORD - And where did you get on the elevator?
Mr. JARMAN - We walked around to the back entrance and went through this door here, and this elevator here was up on six, I believe. And we walked around the elevator and took the west elevator up.
Representative FORD - How could you tell this elevator was at six?
Mr. JARMAN - Because after we got around to the other side we looked up.
Representative FORD - You could see it was on six?
Mr. JARMAN - Yes.
Representative FORD - This was about what time?
Mr. JARMAN - That was about 12:25 or 12:28.
Representative FORD - You got off the fifth floor?
Mr. JARMAN - Yes, sir.
Representative FORD - As you rode the elevator, you noticed the other one was on the sixth floor?
Mr. JARMAN - Right, sir.
Once Jarman and Norman have reached the 5th floor we have the situation where the west elevator is on 5 and the east elevator is on 6. Bonnie Ray Williams is still on 6 as he is yet to join Jarman and Norman on 5. Williams testifies that he takes the east elevator down to 5:
Mr. BALL. Where did you go when you left there?
Mr. WILLIAMS. I went down to the fifth floor.
Mr. BALL. How did you get down there?
Mr. WILLIAMS. I took an elevator down.
Mr. BALL. You didn't go down the stairs?
Mr. WILLIAMS. No, sir.
Mr. BALL. Which elevator did you take?
Mr. WILLIAMS. I took the east elevator down.
This seems to be the state of play when Truly arrives at the bottom of the elevator shaft with Baker - both elevators on 5. The interesting part is Jack Dougherty. As far as I can make it out both he and Bonnie Ray Williams are up on 6 when Jarman and Norman ride up to 5 in the west elevator. The most likely scenario is that he is on 6 when the shots are fired and calls the west elevator up to 6 as Truly and Baker ascend. After Truly steers Baker to the east elevator on 5 (with Williams and co. hiding in the south-western corner) they go up to the roof, missing out the 6th floor, and it is at this time that Dougherty descends to the first floor, drops off his passenger(s), and returns to the 5th.