Select mode for initial sync operation

[Lewis Stairs]

Hi all, 

I recently switched to a new server and obviously the sync data was missing so some users had issues with syncing but that's mostly resolved now except for on one Spoke database, where they are trying to sync data and the error 'One or more of the spoke databases have records in them. You must select a mode for initial sync operation." So I checked on all the usual help pages and found out which initial sync operation mode i would like to use on this one, but I can't find anywhere I can set that? 

I have checked the script and the configuration - could someone point me in the direction of that choice please?

TIA

Lewis