Hi Arkyadeep,
You are adding one month to the result of the previous row. So in your case, you get:
Row 1: 30-11-2020
Row 2: 30-11-2020 + 1 month = 30-12-2020
Row 3: 30-12-2020 + 1 month = 30-01-2021
Row 4: 30-01-2021 + 1 month = 28-02-2021
Row 5: 28-02-2021 + 1 month = 28-03-2021
You can always use the start date from your starting row. So it would be like this:
Row 1: 30-11-2020
Row 2: 30-11-2020 + 1 month = 30-12-2020
Row 3: 30-11-2020 + 2 months = 30-01-2021
Row 4: 30-11-2020 + 3 months = 28-02-2021
Row 5: 30-11-2020 + 4 months = 30-03-2021
Regards,
João