Which license is intended?

[PaulHeitkemper]

The cscore/CSCore.Ffmpeg/License.md begins with the following text:
"License
The CSCore.Ffmpeg project is licensed under the LGPL2.1.
GNU LESSER GENERAL PUBLIC LICENSE Version 3, 29 June 2007

Copyright (C) 2007 Free Software Foundation, Inc. http://fsf.org/

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

This version of the GNU Lesser General Public License incorporates the terms and conditions of version 3 of the GNU General Public License, supplemented by the additional permissions listed below.
..."
So you ostensibly state that it's licensed under LGPL 2.1, but you include the text of the LGPL3.

So which is it?