Update index.markdown

Author: kleinerm

index.markdown

@@ -28,7 +28,7 @@ You can also run some of your Psychtoolbox studies online, via VPixx Labmaestro
 
 Psychtoolbox has many active users, an active [forum](forum), and is widely
 [cited](citations). The current version supports at least Matlab R2024b on Linux, Windows
-and macOS, and Octave 5 and later on Linux, and Octave 7.3 on Windows, and Octave 9 on macOS.
+and macOS, and Octave 6 and later on Linux, and Octave 7.3 on Windows, and Octave 9 on macOS.
 
 Psychtoolbox News
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