You will need to Complete the
Adventure Lab Caches.
I hope that you have enjoyed your walk around Kit Hill. Hopefully you will be pleased that I allowed you to control your own destiny and complete the Labs in what ever order you wish. However it does mean that I have no idea where you are when you get the required information to solve the Bonus cache. I hope you have got somewhere comfortable to sit, whilst you work this out.
During your journey you will have come across 4 dates. Make a note of these and write them down in chronological order.
You now need to substitute either the last 12 or the first 12 digits (once again, you decide) with letters A-L.
You will have 4 digits left over (either the earliest or latest date).
Use these letters in the following formula to locate the Bonus Cache
N50 (H-G) E . A (C - L) (B - L)
W004 I J . (F - K) (K + L) (D / L)