How are you getting different runway lengths for R10 and 28?
it's the landing threshold to the point of the intersection of the runway centreline and the extended exit. Below is the exact details
RY 10
Wingspan less than 36m + B757 preferred exit point on runway is E3* (1690m)
All other aircraft preferred exit point on runway is E2 (2240m)
RY 28
Wingspan less than 24m + all turboprops preferred exit point on runway is E5* (1240m)
All other aircraft preferred exit point on runway is RET E6 (1597m)
*E3 and E5 have visibility restrictions in place
It's preferred exits and ATC should be notified between 4-8NM out or at earliest opportunity if unable to vacate at those exits.