This happens with Mint 18.2 BETA (MATE 64-bit), with the default disk size in VirtualBox. But regardless of what VirtualBox does, or what the installer expects, we should never see contradictory information.
By updating the message (second sentence), the situation could be easily fixed:
"This computer has less disk space than required for the installation".
Or adjust the first sentence:
"You need more than X disk space..."
Anyway, if this is not configurable, the problem depends on the upstream release of Ubiquity.
By updating the message (second sentence), the situation could be easily fixed: "This computer has less disk space than required for the installation".
Or adjust the first sentence: "You need more than X disk space..."
Anyway, if this is not configurable, the problem depends on the upstream release of Ubiquity.