i dont understand the facebook chat mobile sign please help..?

[Luis]

someone told me the mobile sign means they are signed on but how is it possible if i see the same person on facebook chat with the mobile sign all the time every day.. an i mean just the mobile sign an now 2h or 2m or anything like that.. an i also been told that the 2m or 2h means the last time they was to open the facebook messenger app.. im confused

[Prototype]

It means they are on their mobile device, tablet or mobile, and the 2m, 2h, 6h, thing means that they were last active on their desktop or laptop computer then.

[sachin]

It is show time that when they last time active facebook on Desktop on laptop and at present time he/she on mobile and other device...