max_execution time is the number of seconds the php script is excuted. Microseconds is the measure of time ie microseconds and milli seconds and so on..
In your php.ini configuration, you can set the max_execution of your script before your script excution exceeds the execution time. The 108 microseconds converted into seconds it takes less than 30 seconds, so no problem for your script execution
Regards,
Palanisamy