Dear Bharat2018,
Please provide us with adequate background information. Who will be the recipient of the warning letter, why was it issued and whether any warning letters were issued earlier?
When you say "TAT for the final warning letter", do you mean to say the time limit between the two warning letters?
OR
Do you mean to say the time limit for giving a reply to the warning letter? However, this question should not have been asked as an explanation from the recipient is not sought after the issue of the warning letter.
Thanks,
Dinesh Divekar