How much the license for O&K Print Watch will cost you depends on the number of printers that you have added to the O&K monitor.
Suppose you need to manage 4 printers via your print server. In this case, you should use the license for 2–5 printers. Suppose later you add 2 more printers, and the number of printers exceeds the maximum number allowed by your license. Now, to monitor all the 6 printers, you need to switch to the license for 6–20 printers.
When switching the license due to adding more printers, you don’t have to pay the full price of the new license. Instead, you only need to pay the difference between the prices of the new license and the old license.