Hi Sourojit,
I’ve just replied to you via email (with the newest development version 1.4.0 zip attached), but just in case, I’m also replying here.
There are two new options:
1. I’ve added “unit” options for each “rule” – this way you can now set “minutes” for some (or all) of your rules. Available unit values are: seconds, minutes, hours (default), days, weeks.
2. I’ve also added “WP cron interval” option, but as you are using server crons, this option is not really important for you. If anyone else is interested, available WP cron interval values are: every minute, every 15 minutes, every 30 minutes, hourly (default), twice daily, daily, weekly.
Please give it a try and let me know what you think.