This new math just ain't working out for Levi Johnston.
A week after being ordered to fork over $18,500 in back child support payments to ex-fiancée Bristol Palin, the Playgirl poser must find an extra $3,500 in his wallet thanks to an Alaska judge's recalculations.
The payments are retroactive to son Tripp's birth on Dec. 27, 2008, per TMZ. The total Johnston now owes his baby mama comes to $21,561.12
Given the $20,000 Playgirl paid him, perhaps another spread's in order?
Team Bristol is also asking for $1,700 a month in palimony going forward, claiming Johnston earned over $105,000 last year from various media appearances and modeling gigs, including a certain magazine cover. Johnston's lawyer has argued that Levi's income is erratic and he shouldn't be locked in to that amount.
Should Johnston fail to pay up, Sarah Palin's could have been son-in-law may face serious fines for being a deadbeat—possibly even jail.
Of course, Bristol isn't doing too badly herself. She's not only launching her own public relations firm, but she's also making her acting debut on ABC Family's The Secret Life of the American Teenager.
The judge scheduled Sept. 23 as the date for their palimony trial.
Meanwhile, E! News has learned Johnston invited fellow D-lister (and his Teen Choice Awards date) Kathy Griffin to accompany him to a Playgirl signing at Borders bookstore in Anchorage. The two would presumably film their rendezvous for Griffin's Bravo show, My Life on the D-List.
—Additional reporting by Whitney English
Get the full dirty low-down on the Bristol-Levi custody battle here.