What "Render must be in range" error means?

[nicloay]

I have following rows in the log

WARNING:GUI: Render must be in range [0,15]
WARNING:GUI: Render must be in range [0,15]
WARNING:GUI: Render must be in range [0,15]
WARNING:GUI: Render must be in range [0,15]

[AGulev]

I think this warning about:

GUI reference