Frequency refers to the time delay we use to check for new content on a respective feed, e.g. “By every 6 hours” refers that we keep checking for new articles on your provided feed URL at intervals of every 6 hours (4 times a day). If any new article is found, it will be read according to the above mentioned ‘Number of Posts’.
If your RSS publishes a lot of articles every hour, you should select the “Every 6 hours” option.
If your RSS publishes less than 1 article a day, “Every 24 hours” is more form-fitting option to choose.