Website on Voluntary National Insurance appears to contain an error - how to report it?

This web page contains an error regarding voluntary NI for those reaching State Pension Age before 6th April 2016 - ie for men born before 6th April 1951 and for women born before 6th April 1953. According to this page they can pay for voluntary contributions from 2016 to 2018 but that cannot be correct as you won't have any gaps after reaching State Pension Age. The last possible year would be 2015/16. "Pay older gaps in your record (deadline 5 April 2025) You have until 5 April 2025 to pay for gaps in your National Insurance record that were more than 6 years ago. If you’re a man born after 5 April 1951 or a woman born after 5 April 1953, then you can pay voluntary contributions to fill gaps between 2006 and 2018. If you were born before these dates, you can fill gaps between 2016 and 2018." The last sentence is totally wrong. https://www.gov.uk/voluntary-national-insurance-contributions/deadlines?

Hi,
You can report any error on the "Report a problem with this page" link at the bottom of the page. 
Thank you.