According to the Authority, that is the number of users using old, un-updated versions of the ID-software that will loose the ability to digitally sign documents this Saturday.
The technical reason is that an old version of European trust list compatible with older software will finally expire this week.
In case the signing software complains about trust list expiry and/or refuses to sign, the user has to update the ID-software to remediate the issue.
The latest version of the ID-software is available from installer.id.ee.
Only newer versions of ID-software are able to parse newer trust lists.
Corporate users lacking sufficient rights to install the software should call their IT help desks.
There is no need to wait till Saturday, the ID-software could be updated right now.