depends on maps and on devices-
routable maps:
deselect one on your device if they cover the same region-
if the dont cover the same region,rename one of them ,if they have the same name-
or join imgs in one gmapsupp.img with gmaptool in sd (just for some devices)-
topo maps:
usually you can have a topo + a routable covering the same region, but depends on maps-