Jellocan

Me and my friend hid a geocache using a Magellan gps how ever the coordinates are apparently 50+meters off. But when i looked at the coords on google maps it is dead on. Can someone help? Cache:http://www.geocaching.com/geocache/GC62JC8_a-rocky-situation?guid=8adaaa31-f92f-4dc5-abb5-efc7ce14d53f