site:website.com differences on mobile and desktop?

If I search site:website.com on my desktop, I get 6 results and that's it. On my cellphone I've noticed if I do the same but on my smart phone, I get 20 results. I'm just curios if there's something going on that's stopping my my desktop results from getting indexed, anyone know why this is occurring?

Google gives responsive websites priority in search results when people are searching through mobile since it will give them a better user experience.

you need to make a mobile optimization for your website