When you take a capture via the Snapshot button on your Board, it appears as a slideshow in the Export > Gallery menus.
The slideshow of the captures taken is displayed:
You can use the left and right arrows to switch between the snapshots, and the 
to download the snapshot as a PNG or PDF, or discard the one displayed.
Click on the capture to view it in full size:
You can retrieve all captures at once by downloading the data from the Board: Download Activity Data