Use the full LAT and LONG to avoid errors.
If a new NAT track or routing is issued I recommend to enter the full LAT and LONG and let the FMS determine the alphanumeric code for the waypoint. For example enter N5030.0/E03000.0 as a new waypoint and the FMS should abbreviate appropriately. This avoids incorrect data input i.e. 5030N instead of N5030.