B767 Captain reports taking off from Runway 10 at TIST with 5800 FT of runway available. Performance calculations were provided by Dispatch; after takeoff the reporter was informed that there may have been an error.

Narrative

We got the numbers for a 5800 FT takeoff on Runway 10 as was suggested by the Tower. As we were taxing onto the runway for takeoff; we were told that there was only 5700 FT available. I asked where the marker was for 5700 FT; and the Tower said that there was none. I then how will we know how far to taxi - the Tower said that the trucks on either side of the runway were approximately 5700 FT and that we would see the pothole. I then asked where they wanted us to turn around; and the Tower said that we could make our turn just prior to the pothole. So; we went past the trucks and turned around at the pothole. After having completed the turn; the nose of the aircraft was still not back to the trucks. Knowing that the aircraft is 155 FT long; we concluded that we had at least 5800 FT for takeoff. That was the distance that we had for the weight & balance numbers for Runway 10 (5800 FT). After takeoff; the Dispatcher said that we set off all of the company cell phones; insinuating that we had done something wrong. We believe that our takeoff was completely safe and legal.