LOL. I’m on the receiving end of these customs declarations, and stories like this are the reason the copies are so notoriously hard to parse programmatically… lovely, thanks for sharing.
Zero; or an arbitrary number; or a number that was destined for another field, but the commanding officer misread and filled the form wrong; or null; or as many digits as fit in the field. Any of these.
Whatever it is is likely to be part of the endless arms race between customs agencies and smugglers, so I doubt you'll get the privilege of finding out.
And if zero, how often do they just get mistakenly processed as zero value?