Lime for Hazel Truffle Trees

Need to know how much lime to add for balancing out the soil for the truffle trees? Here's a query we got on the email:

"Purchased one of your hazelnut truffle trees and plan to plant it in a large pot - I have purchased 3 35lt bags of soil fron the garden centre and would like to know how much hydrated lime to add to bring the soil up from ph 7 to the required 7.6-9."

I have just spoken to the team that supply our Truffle trees and they say you won't need much, just a couple of good handfuls as you can always top it up.