The first frame has transparency off, and the following 4 frames have WHITE selected as transparent in both sequences.
Frame 1 is shown but has "NO Disposal" selected. Frame 2 then is place onto Frame 1, when Frame 2 is disposed (it is set for Dispose to Background) it removes itself AND Frame 1. Frames 3, 4, and 5 are then displayed and disposed to Background.
Frame 1 is displayed, then Frame 2 is placed on Frame 1 (Frame 2 disposal is set to Previous), Frame 1 reamains when Frame 2 is disposed. As Frame 3 is added it overlays Frame 1, and again Frame 3 is disposed as Frame 4 is added, but Frame 1 remains through all itterations.