The numbers represent 28 pcs of the dominoes laid down on the grid puzzles. (For solution, see <a href="//commons.wikimedia.org/wiki/File:Domino_set_full.png" title="File:Domino set full.png">File:Domino set full.png</a>.)
<a href="//commons.wikimedia.org/wiki/User:Encik_Tekateki" title="User:Encik Tekateki">Encik Tekateki</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>