You just come up with a figure you both agree on. The lawyers if involved just negotiate this anyway. Yes it is based on a calculation but this was adjusted in my case to satisfy both parties.
How much do you need to live on? Look at your bills, etc..

My ex did the same thing as yours. He came up with ridiculous expenditures. He lied and lied and lied. It was very appalling. They will do this, part of the MLC script.

Me: 46 H:44
Together: 25 years
Married: 20 years
Separated: 11-30-06 Divorced 12-21-07
OW: EA began 2005
PA began end of 2006
3 children,20, 16, 6
ex asked for forgiveness
01/16/11