The deadline is floating because, as it is written, it is three days before the last date of the supply period, which is the 26th. Three days before that would be the deadline to report or three days before the last supply day, which at this time we don't know. So this date is unclear. That does not prevent the committee from inviting the minister in question on the supplementary estimates. It's just that the committee would not be able to report officially to the House, but the subject matter of the supplementary estimates can be studied anyway.
That being said, I believe the main estimates are also coming very soon.