The only way to delete maps is to jailbreak the unit and use FMODS’ utilities… We do not support that…
Another way to get rid of the maps (and everything else) is to reformat the unit and install everything again… But since your unit is MY20 you can’t do that with Syn3Updater… You can reformat the unit using FMODS’ universal reformat package that can handle MY20 hardware though…
FMODS has a map delete utility but you must jailbreak the unit to use it. Either way, reformat or using the map utility, requires the unit be jailbroken.