What actually is a subdomain in domain-driven design?

So I was reading the book "Implementing domain-driven design by Vaugh Vernon" and there's something that I don't understand. To make it clear, Let's look at the picture that I took from the book. Here's how he describes DDD concepts such as bounded context, subdomain and etc.

So as you can see in the picture, it describes the domain of a retail company. You have implicit bounded context and also a subdomain inside of a bounded context, but after reading a few pages further I found this picture.

So now it makes me confuse because in the first picture subdomain is living inside of a bounded context, but in the second picture bounded context is living inside of a subdomain (Core, Support, Generic) instead. So what is actually a subdomain that he describes in the first picture. Are they the same thing as the second picture?