We can mention both. Normally, we can only get confirmation at the time of receiving the paysheet from contractors. During October, if you have a confirmed list indicating that the individual will not return for duty in the next month, then you can mention his name in the October return itself. Otherwise, if you cannot get confirmation about whether the worker will come and join in October or not, then you can keep it pending during September and show his name in the October month Form 10.
Hope you have understood the concept. In Form X, you have to provide the date of leaving service. That date can be any date prior to the filing month. In the first week of November, you might have prepared and submitted along with Form V & X, in which you can even include October as well as September. Even for the long-absent workmen, after giving the final notice, you can show their date of leaving service as their last working day. Hence, you can include their names in this return with the last working day for the worker, i.e., in August, July, or June.
Hope you have understood the concept of Form X.
All the best.