Yeah sorry about that, you would never think it from the customer-facing side but Amazon works like molasses in backend inventory stocking (i'm sure with good reason, they do after all sell many, many billions $$ effectively).
Generally, they have the product for a few days before checking it in (Check-in is when it becomes available on the site) then they disperse it as they see fit across their warehouses which takes about a week, then they ship it to the customers. So the whole process takes about 10 days from when a box of inventory is delivered to when they start shipping to customers.
So your kit is sitting on an Amazon warehouse shelf in Dallas Tx, likely to be thrown on a semi truck to a closer Amazon warehouse before they eventually ship it out to you on the 5th.