the first rule and the second are the same?

Question

the first rule says 1. usec'est in sentences it/he/she is + a/the/my... + thing/people but the 2nd says when using If it/he/she is is followed by un/une/le/la - use c'est. - but isnt 'un' 'a' anyway? - im not sure I understand the difference here...

Answer

use c'est in sentences it/he/she is + a/the/my... + thing/people
when using If it/he/she is is followed by un/une/le/la - use c'est
After rereading the lesson, the second phrase of your question is stated after the examples and is a further explanation of c'est.
That being said, the second rule states: "2. Cases expressing opinions or simple statements (adjectives) about previously mentioned things, look at these rules:
a - c'est  for general, unspecific statements and opinions"

I hope this helps.