The VMFS partition on the installation drive cannot be modified from the GUI, but only from the command line.
The required steps are explained in https://kb.vmware.com/s/article/2002461
If you are unfamiliar with this, or unsure please ask back before you do anything!!!
In case you want/need help, please provide the complete output (pasted as text output, not as a screenshot please) of the following two commands:
partedUtil getptbl "/vmfs/devices/disks/<device-id>"
partedUtil getUsableSectors "/vmfs/devices/disks/<device-id>"
André