A partial mobile not-spot is a geographic area served by at least one, but not all four mobile network operators (MNOs). Prior to work starting on the SRN, only 66% of the UK is served by all four operators with 4G.
A total mobile not-spot is a geographic area that receives no 4G coverage from any MNO. Currently 9% of the UK, by geography, is in a 4G total not spot.