This paragraph defines an already defined license.
According to the specification, short license names are required to be unique within a single copyright file.
This tag could be raised by something like this:
Files: filea ... Copyright: 2009, ... License: LGPL-2.1 This program is free software; ...
Files: fileb ... Copyright: 2009, ... License: LGPL-2.1 This program is free software; ...
In this case, you redefine LGPL-2.1 license. You should use a stand-alone paragraph or merge the two files (using a single paragraph).
For more information please consult:
The tag is present in Lintian version
That is the most recent version we know about.
We use semantic versions.
The patch number is a commit step indicator relative to the
release tag in our Git
You can find the detection logic for this version at commit 8ab6976. For merge requests, please use the latest version in the Lintian check debian/copyright/dep5.