First point: the tut letter states that you must visit this forum on a regular basis, since things change very quickly in e-commerce. I have posted a message here that asks you to ignore ProceTag for now, as their server has changed, and to continue with the rest of the prac. So the PriceTag link is not relevant.
The site number that you must claim is to use when you go to
http://osprey.unisa.ac.za/mac/ecom/02/catalog/ (where 02 is the number you have claimed). This is your shopping cart. 02 is mine, so the first person claims 03, the next person 04, the next person 05 and so on. What you claim is what you use in the address here above.
I have open a post here SITE NUMBER. Go there, see what is claimed and then claim the next number. So if you claim 03, your shopping cart is located at
http://osprey.unisa.ac.za/mac/ecom/03/catalog