You can literally gain 1.3in in 6 months. But the amount of work you'll be investing will be phenomenal. That's 14 to 20 hours of extension a day, after 1 full hour of intensive and aggressive lengthening routine. Your traction force will be around 2.75lbs for that entire 14 to 18 hours, and the 30 minutes to 1 hours are being forced between 5lbs to 25lbs of pure traction force to get the micro tears temporary going. 1 hour is to slow the traction force down to 4lbs, and the rest at 2.75lbs.
I was in your shoes in the far past. But once you reached your 6.3in, you need another 6 months to fully cement that length. In reality, to make it permanent, it will be between 9 to 12 monts, or even 15 months where the remaining months are light routines with wrapping, sleeving, or using ADS to keep the elongation in place for gains.