They wanted a nice round number. They'll fill in the rest later. Criterion doesn't release their titles in spine number sequence. Spine number 1 appeared WAY after the ones that are supposedly following it.
That's not exactly so. Generally speaking, Criterion's release schedule proceeds according to spine number, but of course the exigencies of a particular DVD may mean that no. 300 is out before no. 294, which might proceed 297, etc.
The release of "Grand Illusion", or spine no. 1, was delayed for so long because just as they were finishing work on the DVD, a film element in much better shape surfaced... so they scuttled the work done so far, and started over with the new film element.
May is a good month for English-language Criterions, with this, Hoop Dreams & Burden of Dreams all being released. Following "F for Fake" in April, no less. Woo hoo!