As StanMan has said, the ICAO parking stand coding is based upon wingspan and landing gear span.
Stands 7L and 8R are coded:
Code C - wingspan of 24m up to but not including 36m
(all 737 and 737MAX types, all MD80 types, A318 to A321, all Embraer E-Jets)
Stand 7 is coded:
Code D - wingspan of 36m up to but not including 52m
(A300s, A310s, all 757s and 767 types)
Code E - wingspan of 52m up to but not including 65m
(All 777 types, all 787 types, 747-100 to -400, all A330, A340 and A350 types)
One thing to take into account is that each gate also has a set length therefore even though stand 7 is classed as a Code D/E gate, its length limit might not be able to take anything longer than 787-8/A330-200 without obstructing the taxiiway begind.
For example a 65m wide gate (Code E) which has a limit of 61m length due to a taxiway behind length cannot take a 777 without obstructing the taxiway behind.