Hi,

Its not fixed it varies sometimes its even declared after 25 days. Since you gave the exams last month wait till the end of September because that's what they claim in their website

"Every Month through NIOS web site www.nios.ac.in for the ODE conducted during last month.

• After due processing the ODES result will be declared and published through NIOS web site during last week of every month for the examinations conducted during the preceded month."

or get in touch with your NIOS regional center.

Keep a tab on their website for any updates https://results.nios.ac.in/

Hope this was helpful.