The article gives the hypothetical example of redacting a table row

  {zip: 85535, age: 79}

to

  {zip: 85xxx, age: 79}

on the grounds that there are fewer than k (for some tunable constant k, larger = more anonymity) 79-year-olds in zip code 85535, but many more in zip 85xxx. However. If I see the second record, because it has been redacted, I also know that whatever zip code the person actually had, there were fewer than k 79-year olds in it! This may narrow the set of candidates considerably.

So it doesn't seem sufficient to count the mere number of people a redacted row could possibly match. You have to consider the meta-level information that knowing the row had to be redacted gives the attacker.