Waverley is odd that 5 and 6 are still missing after the renumbering. It used to have more missing. To be honest I can't remember what the old numbers on the Southbound end were.
former Platforms 2 and 3, which were latterly used for parcels/mail traffic only and were removed in the 1980s when a new Royal Mail facility was built on their site;
former Platforms 4 and 5 were also retained for parcels/mail traffic until this ceased; Platform 5 was reopened to passengers in 2006 as the new Platform 3;
former platforms 6 and 7, of which only the latter survives, now numbered 4; and
former Platforms 8 and 9, which were substantially shortened for use as a Motorail terminus, the infilled area becoming a car park; since the demise of Motorail services these platforms are used only for locomotive stabling, although the numbers 5/6 were reserved for them in the 2006 renumbering.
The former Down Main through Platforms 7 (east end) and 8 (west end) are at the south side of the main station, and comprise a single very long platform with a crossover in the centre. They are numbered 7 (formerly 10, east end) and 11 (west end).
At the west end there has been little change to the terminating platforms, apart from widening them by removing disused centre-road tracks. The platforms comprise (south-north) numbers 12/13, 14/15, 16/17 and bay Platform 18. These were not affected by the 2006 platform renumbering scheme.
The only platforms outwith Waverley's overall roof are the former 'Suburban' Platforms 8 and 9 (formerly 21 and 20), a lengthy island platform. These are on the southern edge of the station, adjacent to the former freight depot (now a car park).
A need to increase capacity for through and west-end traffic led to three new platforms being built in 2006, on land formerly occupied by disused sidings and bypass lines within the main part of the station. Platform 10 is a through platform at the west end, facing Platform 11. Platforms 1 and 20 are a single long through platform facing Platforms 2 and 19.
Taken from Wikipedia