Looking at the table, if your 'Danger Ranking' is higher than your 'Busiest Ranking' you live in a worse than average area. Forest Hill is exactly as 'dangerous' as you would expect.
However their Busiest Rank is incorrect - taking actual government figures, Forest Hill is busier than West Croydon and Dalston Kingsland, but rated as less busy. This means that Forest Hill is safer than average

Sydenham and Brockley are actually more dangerous than average


Actual Entry/exit Their busiest rank
Shepherd's Bush 1,951,382 3
Willesden Junction 1,688,164 6
Dalston Junction 1,493,502 7
Forest Hill 1,453,318 9
West Croydon 1,392,290 8
Dalston Kingsland 1,322,212 5
Hackney Central 1,205,614 20
Hackney Downs 1,159,414 17
Surrey Quays 1,099,838 13
West Hampstead 1,093,892 16