To make the math easier you can simplify to 7 15 105. In the Insert Sequence Number dialog box click the New button. The sequence number is allocated when NEXT VALUE FOR is called even if the number is never inserted into a table.
Add a number field and give it a title.
It uses SQL functions Row_Number Rank and Dense_rank The Rank function can be used to generate a sequential number for each row or to give a rank based on specific criteria. Each term in the number sequence is formed by adding 4 to the preceding number. Add a number field and give it a title. Something like Purchase Request 1 2 3 and so on.