Products Indexation Priority

I created this product on the 26th of May and it is still not indexed: https://www.zazzle.com/chiropractor_spine_logo_teal_and_gold_appointment_business_card-256463832418024217

whereas this one I created on the 27th of May has just been indexed: 

https://www.zazzle.com/chiropractor_spine_logo_teal_and_gold_appointment_business_card-256463832418024217

I still can’t understand how the order of product indexation works and if there are priorities, I’d really like to know how they work. 

Sorry the second one that has been indexed is https://www.zazzle.com/coastal_sunset_gold_line_art_custom_name_beach_towel-256144070608078442