The numerical pairing of 01 might not mean much to anyone but those who call it binary and use it as a basis for mathematical calculations including computer processing.
But to Hongkongers it can mean the difference between accessing a bank account, completing a property deal or even boarding a plane.
This is because when they renew their home-return permits - the mainland-issued cards they use to cross the border and which serve as identity cards on the mainland - the last two digits of the number are changed to reflect the number of times the permit has been renewed.
Holders run into trouble when they try to use the new cards in situations where they had used the old one such as banking, property purchases and travel.
The problem has recently come to light as the cards, first issued in 1999 to replace the previous passport-like documents, are being renewed for the first time with the last two digits being changed from 00 to 01.
Now the Ministry of Public Security plans to redesign the cards to clear up the confusion, Federation of Trade Unions vice-president Wong Kwok-hing said after a meeting with ministry officials. In future the last two digits may be shown on a separate line instead of appearing as part of the permit's serial number.
