The various atlases available via the whereami function in the GUI have different coordinate systems (different origins and voxel sizes), so the whereami output shows the coordinates for those atlas datasets. These coordinates will very likely not share the same values as the ones output for your dataset from 3dclust.

The Jump to xyz functionality will take the cursor to the coordinates in RAI or LPI depending on the current setting in the AFNI GUI. Right clicking in the upper left of the AFNI GUI where it says "[order: RAI=DICOM]" or "[order: LPI=SPM]" will allow you to switch between one or the other. Because you requested the values in LPI from 3dclust, you may want to switch the coordinates here to LPI also. The current cursor position is shown just below that in x,y,z coordinates by default. It is this position that should match roughly the output of 3dclust, whether it's the CM (center of mass) for that cluster or the maximum value location.