how to find number of formal concept in context formal concept analysis

Question

I want to know who to count number of formal concepts in context.

for example this context:

context

according to my understanding: a formal context is pair of (intent, extent). for our example I could extract those formal concept:

1. ({running},{stream})
2. ({maritime},{sea})
3. ({inland},{stream,lake})
4. ({running,inland}, {stream})
5. ({running,maritime}, {})
6. ({inland,maritime}, {})
7. ({running,inland,maritime}, {})

= 7 +2 because every context has a concept covering the set of all objects and one covering the set of all attributes.

so total is 9 (according to my understanding) ?

Thanks in advance.