I don’t know exactly what you did – depending on your settings. If you used a normative connectome, then it’s basically an atlas, of course, yes. If you used patient specific dMRI data processed in lead connectome, then you could think of it as classical fibertracking from the VTA (although we always first estimate the whole connectome and then select intersecting tracts from that).
Depending on your settings, the E-field is used instead of the VTA (and then tracts are weighted for Efield magnitude). Finally, depending on the analysis, lead dbs sometimes divides all counts by the total number of fibers in the connectome (resulting in small numbers) and even divides it by the size of the VTA (even smaller numbers).
It’s hard to tell what exactly you did from what you write.