How to understand perpetual calendar

For example, if you turn to the year of 20 1 1 this year, the top row of months is the lunar calendar, and the second row of branches corresponds to twelve months, followed by the lunar calendar day (capital) corresponding to the twenty-four solar terms and the corresponding Gregorian calendar day (the number of months and days written); Finally, the corresponding lunar calendar day (only the left column) is: What day is the main branch of the Gregorian calendar day?