Problem using nth-child selector inside table

Problem using nth-child selector inside table

Hello,
I have a problem with the nth-child selector by using it with Jquery.
Normally my code defines what I want, but either there is a conflict between my row and column selections or I do not use the correct selectors or there is a bug in the browsers.

Problems :
A) Friday from 12:30 pm to 1:00 pm should not be in black since the club is open from 8:00 to 21:30
B) the club closes at 19:00 on Saturday - all time slice from 7:00 pm must be in black color.

The problem (A) should not be displayed because I do not select this time slice in my Jquery code
(B) I do not understand why only the slot from 20:00 - 20:30 is selected on Saturday

I describe what I want in my Jquery code if I failed to specify something

The black color means "closed"

Can you help me to find the error? thank you