On an MBR boot how much general space is available on the partitions is largely irrelevant and double check and make sure you actually target the install drive and not e..g the installation USB or so.
]]>grub-Install -target=i386-pc /dev/sda
It return this
zsh: no space left on device: grub-install
But my boot device hase 100MB free space
And also I market as bootable in command
cfdisk