In the book, Into the Wild, what is significant about the cloth belt Krakauer finds in the bus?

The bus is an abandoned one on the Alaska frontier where
the subject of the book, Into the Wild, Chris McCandless spent his
last days on Earth.  He wasn't prepared or trained to survive through an Alaska winter,
and when he got injured (or sick, it wasn't completely clear) he was trying to survive
by eating whatever he could.

McCandless dies of starvation
in the bus.  The cloth belt the author finds when he visits the site must have been made
by McCandless, by hand, while he was laid up in the bus, in order to keep his pants up
on his rapidly thinning frame.  The belt, therefore, is evidence of the grim reality of
his ordeal, and the time it took for starvation to play out.