Why is there a red circle sign on the tombstone in Hong Kong?

There is a red circle sign on the tombstone in Hong Kong because there is a word requirement. According to relevant information, the number of words in the tombstone inscription should be determined according to birth, old age, illness and death, and the last word on the tombstone must fall on the word "birth and old age", otherwise it is not safe. Round means a totem similar to the symbol of the Japanese flag.