In the PDF document "Amazon Instant Access Integration Guide: One-Time Purchases", we are told the following about the size of the pop window for account linking
To facilitate account linking, you must provide an external registration page where the customers can create new accounts (or login with their existing ones) for the third-party software/website. During the purchase flow, we display the page to the customer in a 600 x 500 popup window.
How ever it doesn't say whether it is 600 width x 500 height, or the opposite. Since it doesn't say we can assume the common convention of putting the width first. However if we scroll down the PDF document to the section "Example Customer Flow" we find a sample image of two windows side by side. One for Account registration, the other for Sign-in. The first window looks like it has the dimensions 500 w X 600 h so this contradicts the written information where we must assume that the width is 600. This contradiction could be resolved by looking at the second window. How ever the second window has a totally different aspect ratio that doesn't look like either 500 x600 or 600 x500. So really it is quite confusing. Which is it please?
I asked this question in the support contact page. More than 3.5 weeks later I got a response from someone called Kazumi B. who didn't answer my question at all but instead sent me a link to the online Instant Access Integration guide. This guide does not even include any information as to what size the window should be. Bizarre! I also asked which is the most appropriate forum to ask questions about this. That question went unanswered too. Here is the complete email I received.
RE:[CASE 4935481611] Hex 11 Software[DSV_APP_SUBMISSION][M3EQYOXURA7KAB]
Hello, Thank you for contacting Amazon Vendor Services. This channel is for the Developer submission specific inquiries. For all other inquiries, please contact from below: https://www.amazon.com/gp/help/contact-us/general-questions.html?referral=A25D1OO900VP46_A152YKYEZA4TCR? However, I've found a forum submission for the related inquiry (no answer yet) that you can follow and add comments: https://forums.developer.amazon.com/questions/16545/info-on-amazon-instant-access.html This support contact is being closed. If you have any additional questions please open another contact. Thank you for your understanding, Kazumi B. Amazon Seller Support