hello can you help me to understand this. 4 (18) it's 2 dots (19) 3 dots (20) 6 dots (21) 4 dots (22) 1 dots (23) 1 dot (24) ??? I don't get it

hello can you help me to understand this 4 18 its 2 dots 19 3 dots 20 6 dots 21 4 dots 22 1 dots 23 1 dot 24 I dont get it class=