When the FREQ option is set to DAILY, the INTERVAL will be counted on a daily basis. All days in the week will be taken into account in the interval calculation logic. The BYDAY option will not be taken into account when positioning the occurrences against the INTERVAL, but it will be applied as filter after the intervals have been calculated.
Calculating only the interval, in the discussed scenario
the 4 occurrences will be set on 16, 19, 22 and 25. Nevertheless, as BYDAY option is also used, it will be taken into account after calculating the above rule. Therefore, the last occurrence, which is on Sunday, should be shifted with 3 additional days. Therefore, it will be displayed on 28th.
If you think that the current recurrence rule calculation logic could be improved in some manner, I would suggest you to log you idea on our Feedback portal
. Based on the support it receives from the community, we will decide on whether to proceed with its implementation or not.
I hope, that the above explains the case. If you have any other questions, please do not hesitate to contact us.