Sidework Law

I'm new to the industry, serving for about 2 months now at a local chain that is franchised. I've read some posts on here about a law where if you do more than 30 minutes of sidework, you are supposed to get paid full minimum wage. I have heard nothing about this at work or from my coworkers, though. At my restaurant, I typically do 60-90 minutes of sidework once I'm cut, and that seems to be the typical amount for all servers. On my pay stubs, I'm only getting paid my tipped minimum wage for all hours worked. Is this something I should be concerned about?