What is the Verification No.?

I have had a few people who have had difficulty contacting me via this contact form and asking what a Verification Number is.
The little box just above the “Send Inquiry” button displays several characters made up of letters and numbers with a zigzag line through them. This is the Verification Number, and should be copied exactly at shown in the empty box above it – remembering to include upper and lower case letters where relevant.