You need to work the answers out, then you do the sum at the end to find the cache.
1. The month (number) of Harry's birthday? A
2. Harry's age in his fifth year at Hogwarts? BC
3. Sirius Black's prison number? DEF
4. How many items does Hermione throw at Hagrid's hut in the third film? G
5. The number of the platform the Hogwarts Express leaves from rounded to the nearest whole number? HK
6. The number of staircases at Hogwarts? MPR
7. The number of rings on a Quidditch pitch? S
8. The number of children of Mr & Mrs Weasley? T
9. The Number of Harry Potter books including the comic relief books? U
10. The number house Harry lives at with his aunt and uncle? V
11. Number of Grimmauld Place that Harry arrives at in the 5th book? XY
Once you have all the above information you need to solve this equation.
N 51 (V-Y)(U-E).(S-V)(C-B)(T-C+X+D) W 000 (A-P)(D+F).(G+H+K+R)(R+S)(M)