Permitted Route for Boundary Zone 6 Ticket?

[hkstudent]

I am planning to get a Day Travelcard on London Zone 1-6 and plan to visit a Southwestern Station.
However, given to the complexity of Southwestern's network, there are multiple Boundary Zone 6 stations are available to chose from.
Is there any documentation that dictates my choice of Boundary zone station and routings?

For example, can I use a Boundary Zone 6 ticket at Surbiton to go to Virginia Water, instead of travelling from Feltham?
[Of course, there are some more outrageous case like Coulsdon South to Virginia Water which is also a Zone 6 station]
If I break the journey at a station (which is deemed not that reasonable), will I be having any troubles?

 

[yorkie]

It's the same calculation as a ticket from the relevant station.

There are numerous existing threads on the topic.

If you plan the journey into London on reverse, and a booking site offers it on one Travelcard, it's valid. If not, it isn't.