The estimated numbers comes from a note from KGI Securities analyst Ming-Chi Kuo, according to Business Insider. In the note, Kuo reportedly believes that the reason for the short supply is due to a low stock of three parts for the phone including issues with circuit boards and a camera modules.

The last time Apple reported its preorder numbers was in 2014 with the release of the iPhone 6 and 6 Plus. The preorder numbers broke records selling over 4 million in the first 24 hours, according to Apple. KGI Securities reportedly reduced its forecast for Apple fourth quarter shipments to 25 to 30 million units, down from 30 to 35 million, Business Insider reported.

Preorders for the iPhone X start Oct. 27 before the phone becomes available on Nov. 3. Some of its iPhone 8 models began selling out within hours of pre-orders launching. The iPhone X is the most advanced smartphone Apple has put out, and marks the iPhone’s 10th anniversary. The cheapest model is $999.