It's not a tracking number. It is a bookkeeping number for Canada Post. Until recently the same number was the insurance number for Small Packet. On Expedited (and other Delivery Confirmed services) it is the DC number. On a few expensive services (Priority Post) it is a tracking number.
Don't worry about it.
Small Packet is neither insured nor "tracked" (PP only requires Confirmation of Delivery, but call it tracking. Rather like the White Knight's Song in Alice in Wonderland, actually.). But it is fast and reliable.
Give the (useless) number to your customers. They will be reassured that you have purchased postage and probably mailed the parcel on the purchase date.
You can self-insure by adding a few cents as an insurance premium to every shipping and handling fee you give. Then if you ever lose an item to slow delivery or damage, you can use the accumulated pennies to refund your unhappy customer without getting PP punishment involved.
