"The first thousand people to sign up using the link in the description will get their first two months free."
This is a sentence from a sponsored Youtube video. I saw it and wrote it down. My question is, what is the difference if we place by after "to sign up"?
Someone on the Internet I talked to suggested that adding by could mean that there are other ways to get the incentive, while not adding by could mean using the link to sign up is the only way to get the incentive. I am not sure if my question is subjective to the individual.