Test it: Take a strip of paper cover half of it. Expose it for maximum black, by turning the lights on for a few seconds.
Cut that strip in smaller pieces including the exposed as well as the unexposed part. Develop the parts for 1, 2, 3, 4, 6 minutes. Examine when wet: Which one reaches maximum black? Examine when dry: Any fogging?
Keep your time above the time for maximum black and well (!) below the value were fogging sets in. If fogging is a concern you better expose for three values, unexposed, light gray, maximum black.