You will need to Complete the 

Welcome to Kit Hill Bre Skowl a'gas dynergh 

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)