[TYPO3-english] update wizard -> changeCompatibilityVersion; configured to behave like version 4.1 of TYPO3

[Rupali]

Hello List,

we are using Typo3 4.2.6 on one of our Projekt from beginning and today i
saw following warning:
This installation is not configured for the TYPO3 version it is running. If
you did so intentionally, this message can be safely ignored. If you are
unsure, visit the Update Wizard section of the Install Tool to see how TYPO3
would change.

what does it mean: " configured to *behave like version 4.1* of TYPO3" and
why localconf is showing $TYPO3_CONF_VARS['SYS']['compat_version'] =
'4.1'; when we had downloaded typo3 4.2.6 ?
Was there any problem while installing (then what ) or any new reason (any
bug)?

Thanks!