You're not getting paid to work during this time. If this will help you in your career in general, e.g. you'll learn technology skills that will also be releva

You're not getting paid to work during this time. If this will help you in your career in general, e.g. you'll learn technology skills that will also be relevant to future jobs, then doesn't seem like a problem. But if this is company-specific learning that won't translate to future jobs, you're basically starting the job with the clear message that you will do work for free. This is bad. It's important to set boundaries from the start, or bad managers will have you working long hours.