If you want a combination of 6 two-digit numbers, that is 12 digits. So let's assume that you want 4 times 0, 3 times 1, 2 times 9 and 3 times 5, that is 12 all together. Now you need to arrange them into pairs to make numbers. I think that it will be easier to compose numbers 0..59, instead of 1..60, so in the end, you take 0 (i.e. 00) for 60.
Start with a line:
0,0,0,0,1,1,1,5,5,5,9,9
Here, you only have 10 digits (0, 1 and 5) which qualify for the first digit in numbers below 60. So you first choose 6 digits to take positions of the first digit in each number.
For a start, you choose a random number from 1..10. E.g. you get 5. You have digit 1 in the place number 5 (marked red), so you take it out. That will be the first digit of your first number. What is left is this:
0,0,0,0,1,1,5,5,5,9,9
Now choose a random number from 1..9. E.g., you get 3, where you find digit 0, so the first digit for the second number is 0. This is now left:
0,0,0,1,1,5,5,5,9,9
Etc. Let's say that you end up fith the following digits: 1,0,5,1,5,0
So, now you are left with a sequence:
0,0,1,5,9,9
For the second digit, all digits qualify. So you now choose a random number from 1..6. E.g., you get 4, which gives you digit 5. Etc.
Let's say that in the end, your second sequence is 5,0,1,9,0,9. This gives you your final combination:
15,00,51,19,50,09
This one is OK, but it could happen that the same number appears twice, so you might need to swap the last digits of two numbers in the end.
Start with a line:
0,0,0,0,1,1,1,5,5,5,9,9
Here, you only have 10 digits (0, 1 and 5) which qualify for the first digit in numbers below 60. So you first choose 6 digits to take positions of the first digit in each number.
For a start, you choose a random number from 1..10. E.g. you get 5. You have digit 1 in the place number 5 (marked red), so you take it out. That will be the first digit of your first number. What is left is this:
0,0,0,0,1,1,5,5,5,9,9
Now choose a random number from 1..9. E.g., you get 3, where you find digit 0, so the first digit for the second number is 0. This is now left:
0,0,0,1,1,5,5,5,9,9
Etc. Let's say that you end up fith the following digits: 1,0,5,1,5,0
So, now you are left with a sequence:
0,0,1,5,9,9
For the second digit, all digits qualify. So you now choose a random number from 1..6. E.g., you get 4, which gives you digit 5. Etc.
Let's say that in the end, your second sequence is 5,0,1,9,0,9. This gives you your final combination:
15,00,51,19,50,09
This one is OK, but it could happen that the same number appears twice, so you might need to swap the last digits of two numbers in the end.