Look at the screenshot:
Do you see, that the amount of sessions, generated by new users, is lesser then the amount of new users?
How can it be? Are there new users, who don't created sessions? If yes, what are such users? Bots?
It's possible for the value of the metric Sessions to be less than the value of New Users. The reason is that Sessions is not incremented in cases where a session only consists of non-interaction events. In contrast, New Users is always incremented when a new-user session occurs, even if the session only consists of non-interaction events.