Well, 918 million is just a tad less than one billion and one billion is 1,000 x 1,000 x 1,000. So... imagine a cube where the length, width and height were each equal to about three football fields plus just shy of three end zones placed end to end (324 yards or 972 feet). That would be about the size of it....
That’s still a frikken mountain of rock. Scary.