The PNG spec says that the length of a "chunk" (their term, not mine) is specified in the first four bytes of the file. When I read it in, the first four values are :
0 0 32 0
and the length is almost certainly not 32.
A smaller chunk that was 4 had its first four bytes as:
0 0 0 4
What is the weighting given to these values (if that even is the right question to ask)?