How much did Calpurnia give Jem and Scout before she took them to the church?
The answer to this question can be found in Chapter 12. I think that the answer you are looking for is that she gives each of the two kids a dime. The point of that is that they are going to put the dimes in the collection basket as donations.
The reason I say that I think this is the correct answer is that she gives them the dimes once they are already inside the church. The service has not started yet, but they are inside the church.
When she gives them the dimes, they say they already have dimes to give, but she says they will take hers because they are her company.