The following properties appear multiple times in the jbossjta-properties.xml file (there may be other duplicates I haven't noticed):

<property
name="com.arjuna.ats.arjuna.recovery.periodicRecoveryPeriod" value="120"/>
<!--
Interval in seconds between first and second pass of periodic recovery.
Default is 10 seconds.
-->
<property
name="com.arjuna.ats.arjuna.recovery.recoveryBackoffPeriod" value="10"/>
<!--
Periodic recovery modules to use. Invoked in sort-order of names.
-->