Compare the bottom line of both images.
It should never be empty.
This tip for calamares (our installer) only concerns people
- that have older hardware and use MBR to install ArcoLinux
- that use Virtual Box and use MBR to install ArcoLinux.
EFI or UEFI people are NOT affected and do not see the bottom line about the boatloader in Calamares.
If you do not change anything, then the installation will go fine.
If you change the settings in Erase disk from no swap to anything else then Calamares (may 2019) will have forgotten the last line and you will have to add it manually yourself.
See images and video.