No options to try Ubuntu or install Ubuntu

I’m trying to dual boot my Dell XPS 15 7590 running Windows 10 Pro with Ubuntu 18.04. After booting the live USB with try Ubuntu without installing or install Ubuntu I cannot actually install the OS. I’m using a 8 GB USB stick, but I cannot select the 128 GB partition I created before. I could only select a language and keyboard layout before this error message shows up: “You need at least 8.6 GB of free space to install Ubuntu. This computer only has 8.0 GB.”

Any idea what I could have done wrong?