The First Minister of Wales Mark Drakeford has stated Wales are slowing down the delivery of the Pfizer vaccine so they can space it out evenly over 6 weeks, rather than administer it as soon as possible pic.twitter.com/Sl4xiS6qUc
I'd imagine its because they cant work out the logistics of administering all 900+ doses from one box at one time. In Scotland theyve worked with Pfizer to work out how to safely work with smaller batches.