That is because your String resource has multiple %s or similar. To avoid this, you must identify each like this: %1$s. Example:
<string name="full_name">First: %1$s - Last: %2$s</string>
Where %1$s is your first substitution and %2$s is your second.
If you do not mean to perform any substitution, just add the attribute formatted="false". Example:
<string name="your_string" formatted="false">Level: 100%</string>