Petman,
While I agree with Sara Anne that the three weeks difference is unimportant, I thought you might like to see the reasoning behind the timing of treatment in the Dr. Lamm Schedule. Dr. mike O'Donnell is one of my trusted authors on BCG and bladder cancer.
The FAQs, including timing discussion, starts on about page 13 of the following.
thomaschallenger.com/wp-content/uploads/2011/10/Mike-ODonnell-Protocol-long.pdf
Best,
Jack