Calculations for Gua or Kua numbers are different for a male or female. Simply use the last 2 numbers of your birth year.
For an male:
EX: A male born in 1965
Add the last two digits of the year of birth: 6 + 5 = 11.
Bring it to a single digit number: 1 + 1 = 2.
Deduct your single digit number from number 10 => 10 - 2 = 8.
If you get a 5 revert the number to a 2
For a female born
EX: A female born in 1965:
Add the last two numbers of your year of birth 6+5=11
and bring it to a single digit 1+1=2
Add your single digit to number 5 +> 5 + 2=7
If you get a 5 revert the number to a 8
You will get a number between 1-9, again if you get a 5 then you follow the instructions on which number to use.