It means to the best level of confidence one can have (given many factors)...we are slowly walking UBL into a smaller and smaller area of operation. No need to go into specifics but such a process takes a great deal of time and there are multiple intertwined (systematic) processes / procedures which are implemented to make this happen.
And once one understands this region of the world (terrain, customs, etc) one has an easier time understanding that while you may not certainly be able to pin-point an individuals location....you can have ways of putting someone in a "zone" within this region (to a high level of probability).
The reality is time was on UBLs side in the short run to avoid capture / being killed in this region of the world.