Here I found the meaning of the 7th day of the Lunar New Year means
Seventh day, zhengyue 7, ‘Birthday of Men’
The seventh day of the first lunar month is named renrì (Traditional Chinese: 人日, Pinyin: rén rì), literally Human Day and is considered to be the birthday of ordinary, or common men. The day is also called Day of Men or Men Day.
According to Chinese legends, Nüwa (Traditional Chinese: 女媧; Simplified Chinese: 女娲; Pinyin: nǚwā) is the goddess who created the world. Two legends refer to her creations.
Nüwa and her brother Fuxi survived a devastating calamity, which had wiped out all other life. Retired to Kunlun Mountain they prayed for a sign from the Emperor of Heaven. The divine being approved their union and the siblings set about procreating the human race.
Note: in some texts or according to other legends, Nüwa is considered to be Fuxi’s wife.
According to a different legend Nüwa created certain animals on different days as she was lonesome and wanted the animals as company. On the seventh day after the creation of the world, Nüwa created human beings from yellow clay. With the divine power entrusted to her, Nüwa made the clay figurines to become alive.
Renri is the day, when all common men are growing a year older and the day is celebrated with certain foods according to the origin of the people.
The ingredients of the dishes have a symbolic meaning and they should enhance health.
To honour Nüwa's creation of animals either vegetable dishes will be eaten or a raw fish and vegetable salad called yusheng (simplified Chinese: 鱼生; pinyin: yúshēng).
Yusheng literally means "raw fish" but since "fish (鱼)" is commonly conflated with its homophone "abundance (余)", Yúshēng (鱼生) is interpreted as a homonym for Yúshēng (余升) meaning an increase in abundance. Therefore, yusheng is considered a symbol of abundance, prosperity and vigor.