Model numbers can be a little confusing, due to the fact that some retailers have an arrangement with the manufacturers. Take as an example the DSG Group, PC World for instance. If you check some of their printer range, you will see a model number change by one digit, yet the product is identical to those that have come off the same production line for other retailers. This is a form of identification for (in this case PCW) DSG Group.
Why not ask the store in question, for the reasons why?.