For what it’s worth, I’ve been paid monthly since I started working (1974) and I’ve never been paid less than 1/12th of my annual salary regardless of at what point in the month the company decided was that payment date.
However, don’t be shy, as an employee you have the absolute right to ask for clarification as to how much you’ll be paid. And if they don’t want to answer, or are snotty because you ask, well ask yourself, do you want to work for people like that?