You should discuss this with your attorney so your attorney can make sure that everyone has the same understanding of what "after taxes" means.
"After taxes" generally means the amount that remains after subtracting the amount by which the distribution increases your ex-husband's tax liability, That has nothing to do with the amount that your ex-husband has withheld from the distribution for taxes. Tax liability and tax withholding are two different things. For example, if the distribution is $1,000 and it increases your ex-husband's tax liability by $220 because his marginal tax rate is 22%, using this method your ex-husband would be paying you $780 no matter how much of the distribution he has withheld for taxes.
