NOt sure if this is the right place to post this?

I'm sure this is easy but I am having trouble getting my head around it.
I have a table based on the following :

Client purchase date order number
A nov 05 1
A nov 04 2
B jul 05 3
B nov 05 4
C mar 04 5
C nov 04 6
C jul 05 7

I have created a PT that counts the number of orders by each client eg.
A 2
B 2
C 3

But I would like to be able to count the number of clients who have
purchased once, twice, three times etc. So I guess I am trying to count the
totals from the count of order numbers - but I cannot seem to get it.

thanks