New installations may run on a temporary serial number, if a telephone connection to the provider can not be established at the time. The temporary serial number can only be given once and runs out after 28 days. I.e. after 28 days, you cannot enter another temporary serial number; if you try to do so, SIHOT shuts down and can not be started anymore! Therefore, you must obtain a final number by your provider as soon as possible, thus ensuring continuous access to your installation.
The field expire shows you when this temporary serialisation runs out.