That's correct. There are various opinions of what the minimum distance should be, but most people agree on 100 feet. That's Futaba's opinion as well. They have written an excelent guide for range checking in their FAQ's, including a few things to check if you don't achieve 100 feet during your range check.

http://www.futabarc.com/faq/faq-q331.html

Reminder - have someone hold the plane while performing the engine running range check, or secure it well enough to hold the plane at full throttle.