The items listed ARE in numerical order… for the filtering you have selected, because you choose “Only High chance”.
What the missing numbers means is that there are better upgrades OVERALL available, but if you want to get items quick, you only see which ones you can GET quick… if you want to take chance of waiting for better upgrade, then list will show more items - you need to decide; “do I want to get GOOD upgrade (that take long time to get) or take OK upgrade that you can get quickly?”.
Right hand side info. might be missing if drop in content you don’t want to do (M+ Dungeons, etc).
Site dev’s - please help me out if I’m wrong…
Yeah eighjan has it right – your rarity filter has a bunch of items hidden. Those other items would be upgrades, but have a lower drop chance.