One questions ask what to do with a PCT app where there were two missing parts of the spec, and the applicant filed them at two intervals. The international filing date will be the date the timely filed filed correction is received by the receiving office. MPEP 1810
Answer: There are only 30 days to do this, and so his 2nd submission was not entered.
Consult PCT Rule 20.6 for more details about this specific question, and 20.7 for the time limits for various other situations.