Field help (GAFPER) 

The frequency of the recurring journal is mentioned in the form of a number or a time unit.
In the case of a levelled recurring journal, the frequency is necessarily monthly.

It is possible to define the recurrence of the open items of the recurring journal to: every n days, weeks, decades, months etc.

In the case of a levelled recurring journal, the open items can only be settled/received in monthly payments.