Do people in the US really tip another 10-15% after the bill already says 15% gratuity? (Update: seems like majority of the people are from r/tipyourserver and are pretending to be customers to influence this post and the people who will see it in the future so they can keep getting tipped)

So I’m from Australia and tipping is not part of our culture except for maybe a small amount (5-10%) for good service at a more premium restaurant. It’s just normal to pay what’s on the bill. <br><br>I have recently been to the US and had a few experiences where the bill already says gratuity 15% (compulsory tipping). I asked the waitress if we needed to give more and she said so the total comes out to $X so please give that amount. Then I asked her how much extra should we give and she said oh you don’t have to but anywhere from 10-20%. I thought that was already included in the bill but I believe her because she is the one serving me. To me that’s a total of 25-35% of the bill is that normal for the US? Do you add an extra 10-20% ontop the bill and also pay the 15% gratuity? I thought it was already included in the bill.