Why does the TfL journey planner suggest taking two trains and a bus from
Lewisham when I want to go from Charing Cross to Bluewater Shopping Centre?

One journey suggested is

11:22 Charing Cross Rail Station
Take Southeastern towards Gillingham (Kent) Rail Station

12:19 Greenhithe Rail Station
Take Southeastern towards Charing Cross

13:32 Lewisham Stop: G
Take Route Express bus 022 towards Harbour

Bluewater Bus Station
Walk to Bluewater Shopping Centre

14:05 Bluewater Shopping Centre

But if I read the Southeastern timetable correctly the 11:22 form Charing
Cross goes directly to Greenhithe for Bluewater.

Question number 2:
How can I find out how much this journey (Charing Cross - Greenhithe) will
cost me? I have a 7 day zone 1-6 travelcard on Oyster.

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jhk