Despite its name, this element is used to specify the API Level,
not the version number of the SDK (software development kit) or Android platform.
The API Level is always a single integer.
in 2 words:
api-level (not android version)
only integer (not float)
An integer designating the minimum API Level required for the application to run.
The Android system will prevent the user from installing the application
if the system's API Level is lower than the value specified in this attribute.
You should always declare this attribute.
An integer designating the API Level that the application targets.
If not set, the default value equals that given to minSdkVersion.
An integer designating the maximum API Level on which the application is designed to run.