Adventure pro Maximum size of a trail system that i can import?

WHAT is the max size of a trail, that I can import. 

I started at 47 megs, and no. I have been chopping up my trail down to 21 megs and i still cant get the Adventure pro to see it on the SD drive. All of my other trails 1-2- or 3 megs no problem. I'm trying to put Bob T maps of Hatfield's and McCoy's in it in GPX format.

My samsung tab works fine. BUT my  Adventure Pro wont let me put the whole system in.

PLEASE HELP