To upgrade the multiplier from 1000 to 1500, you need to collect enough gems and fill the gem slot shown in the upgrade window (on the right side of the upgrade rune)

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2764140883

yes, there are enough of them.
I wrote that there was a problem with it.

thanks for your screenshot, we'll fix it soon

i found and other issue with steam achievements

i shoot 100k in one session but the achievement doesn't count and my game crash when i go back to harbor