In this case, answering that you feel any amount of burnout (including "To a small extent") to the prompt "I feel burnt out from work" means you suffer from burnout. In fact, the distribution from most burnt out to zero was: 21%, 34%, 28%, 17% - a relatively even distribution. An alternate headline (that's less exciting) is: 45% of software developers barely suffer burnout. That's almost a coinflip.
I'd be shocked if this doesn't just mirror the general population.