Using a Bitcoin-Qt v0.16.0 (downloaded from bitcoin page) in an macOS High Sierra 10.13.4
When I start after a fresh install Bitcoin-Qt as a mainnet node and wallet, the wallet prompt that about 203gb is going to be used in my disk
When I start the node and wallet as testnet, shows the same message about the 203gb disk usage
It seems that the second time the message is wrong, due that the testnet database uses about 14gb.