What is the negative pressure in this negative pressure type carburetor?

“It is the negative pressure in the engineʼs intake system. The advantage of this carburetor is how smoothly it responds to the riderʼs throttle work. With this carburetor, you will rarely experience any sudden or unexpected jolts of acceleration or deceleration, even if you are not particularly conscious of the engine rpm or running conditions at the time of a throttle action. This is because of the “butterfly valve” on the engine side of this carburetor that moves up and down with changes in intake pressure to effectively vary the size of the air-fuel mixtureʼs intake passage and thus regulate fuel supply. Also, the FZ16 has a throttle position sensor (TPS) to enable 3-dimensional control of ignition timing based on changes in engine rpm and throttle opening for better running performance and fuel economy.”