The percentage basis is your current basis (Line 14 of your 2021 Form 1099-R plus the amount that you've contributed for 2022) divided by your current total balance in traditional IRAs. However, you don't need to calculate the percentage. You just need to move the pre-tax amount (total balance minus basis) to the 401(k). You are not permitted to move any of the basis to the 401(k), so on the day of the distribution that is rolled over to the 401(k) you must leave an amount in your traditional IRAs that is equal to the amount of your basis.
If your current basis in traditional IRAs is $13,924 and your current balance in traditional IRAs is $50,000, yes, the pre-tax amount in your traditional IRAs is currently $50,000 - ($13,924 + $6,000) = $30,076.
