These estimates are based on a universal basic income paid for by increasing the federal deficit. As part of the study, the researchers also calculated the effect to the economy of paying for the cash handouts by increasing taxes. In that case, there were would be no net benefit to the economy, the report finds.
This is a pretty important part of the study and a good example of why its results don't mean very much.
I support a universal basic income, but not implemented like this.
Kill 1 man: You are a murderer. Kill 10 men: You are a monster.
Kill 100 men: You are a hero. Kill 10,000 men, you are a conqueror!