Ok I have a new Icon on this empeg that I don't remember having on any of my other ones.

Up in the upper right hand side is a small square from time to time it will pop up and have a light colored line or a dark colored line or be fulled any idea what this is ? (so far only happens on house power Empeg is not installed in car yet)
I am thinking it might be the memory full status buffer but I don't remember this icon