5:13 PM PT -- Britney's lawyer, Laura Wasser and Kevin's lawyer, Mark Vincent Kaplan just left the courtroom after a closed hearing. Sources say nothing substantive was decided and all hearings regarding Kevin's request for child support have been put off until a later date.

Britney Spears' legal team is about to square off with Kevin Federline's in an L.A. court, and the central issue is going to be whether Kevin needs additional child support for the 2 kids he had with Britney or whether it's because he's trying to get her to support his other 4 kids.

As TMZ first reported, Britney has been paying Kevin $20k a month in child support for years. In addition to the support checks, we're told Britney pays for the kids' tuition and related school expenses, clothing, extracurricular activities (including sports), and various other expenses. In all, she forks over around $35k a month.

Kevin's lawyer has reportedly demanded $60k a month ... which Britney and her conservator, Jamie Spears, have refused to pay. We're told Jamie is agreeable to raising child support by around $10k a month, despite the fact he believes Kevin doesn't really pay for anything related to the kids.

Friday's hearing, we're told, could get contentious because Britney wants to cut to the chase and figure out what, if anything, Kevin really needs for the kids. We're told Kevin's lawyer wants to comb through all of Britney's contracts to determine exactly how much she makes and spends.

We're told Britney's team thinks it's ridiculous Kevin's lawyer wants to go through the time-consuming and expensive exercise of figuring out what she makes because everyone knows she makes a fortune, so the only issue is how much more the kids need. Her team believes the only people who benefit from dragging this out into an expensive process are the lawyers.