Can anybody explain why Chromium tech writer chose to sprinkle "up to" everywhere in the numbers? For example: "we’ve improved browser responsiveness by up to 9

Can anybody explain why Chromium tech writer chose to sprinkle "up to" everywhere in the numbers? For example: "we’ve improved browser responsiveness by up to 9%". This makes the article so confusing to read. Does it mean browser responsiveness improved by 0.1% on average, and in some very edge case, it improved by 9%?