How to read the flag signals?


#1

Hi, everyone. I am a student in maritime training school.
My textbook published by Ministry of Education has two examples:

C
G
3
1
First substitute
0

it says this hoist means “CG3130”, and the other one

A
2
First substitute
Second substitute
Answering Pennant
Third substitute

means “A222.2”.

Should not be “CG31C0” and “A2A2.A”? It makes me confuse.
Does it miss a Tackline under G and A?


#2

The substitute only repeats the immediately proceeding class of signal (letter or number). Here’s the page from the International Code of Signals that explains this: