Norway train ticket info

Trying to book online at Norway's train company NSB. One of the items asked for is a mobile number but it can only be 8 digits long. USA numbers are 10 numbers. It is a required item. What number can I use? Can I pick one of the hotels we're going to? Has anyone in the USA used this site? Thanks.

The number is just used as a customer number in combination with the travel reference - you'll need it when picking up your ticket. Feel free to use any 8-digit number, such as the 8 first digits of your own number.