That number must be written on the invitation. Normally local travel companies will only issue an invitation for those days that you have paid for as you are their responsibility until you leave their country. However there are a number of travel companies that are willing to just send you the invitation and the rest is up to you, although as you have to be registered, you must visit the company that issued you the visa and it is best to do this as soon as you arrive. Normally, faxed invitations are accepted by the consulates. Visa Information Visas to Belarus are required by virtually all nationalities including Americans, Australians, Britons, and Canadians.
Visas have to be obtained before arriving in Belarus.
As of 1 April 1995, visas were no longer issued at Miensk-2 International Airport or at the border crossings of Brest and Hrodna. Russian visas are acceptable for transit through Belarus such as on the Warsaw-Moscow train. However if you are travelling from Moscow to Brest, and hoping to buy a cheap suburban rail ticket from Brest to Warsaw, you will only be sold one if you have a Belarusian visa. There is no border control on the Belarus-Russian border. This poses a problem if you have entered Belarus on a Belarusian visa as your Russian visa will be unstamped when you enter Russia and you will not get a customs form.