@riffmax, good questions!

Your first stop for a lot of answers should be here: https://us.fotolia.com/Info/Contributors

There are two ways to purchase images, credits or subscriptions. Credits are the currency used for individual purchases and Extended licenses. One credit = $1 if your account is in the US zone. Your commission based on credits sales is determined by your rank. Your rank is determined by the quantity of sales you have. The more you sell, the higher your rank. The higher your rank, the higher your commission: https://us.fotolia.com/Info/Contributors/Royalties

Subscriptions are used by customers to download multiple images. Most subscriptions are monthly. You are paid a flat rate of 33% of the price paid per image regardless of your rank. All Adobe Stock sales are paid as subscriptions.

When you reach $50 in your account you can submit a payment request using either PayPal or Moneybookers (Skrill). You will need to have a current, government issued ID card on file to process this request.

Why has one specific image been the one selling for you? That is a subjective question, sounds like you have an image that stands out and is meeting the needs of multiple buyers. Without being able to see your portfolio it's pure speculation.

Weekly ranking is based on your entire portfolio, not individual images.

I hope that helps, good luck!

-Mat

Thanks for the reply - that's quite helpful.