Hi Kamil,
I am happy that you have tested the plugin and posted the results. It will also help you to test other free and premium themes.
Is that ok? Or shall I fix something?
Short answer is – It is Perfect
Long Answer
REQUIRED:
Theme Check result should not throw any REQUIRED output. If theme check result is free from REQUIRED output, than the theme is perfect and according to WordPress coding standards.
WARNING:
Same as REQUIRED. There should not be WARNING output by Theme Check plugin.
In your case, Theme Check has detected an error_log file by PHP. Find this file and delete it.
* This file is not the part of our Theme Package
RECOMMENDED:
No need to worry,
Screenshot size should be 880×660: This rule has been added recently after the launch of WordPress 3.8. So we will update theme screenshot in the next version.
INFO:
No need to worry.
Thanks