"In California there is a 'statewide uniform guideline for determining child support orders.' (Fam. Code, 4055, subd. (a).) This guideline is an algebraic formula. (Ibid.) The intention of the Legislature in adopting the uniform guideline was 'to ensure that this state remains in compliance with federal regulations for child support guidelines.' ( 4050.) The court may depart from the guideline only in 'special circumstances' set forth in the child support statutes. ( 4052.) 'When ordering child support the trial court lacks discretion to vary from the presumptively correct amount, calculated by applying the algebraic formula in the statute, unless one or more of the statutorily enumerated rebuttal factors is found to exist.' . . . "There is a rebuttable presumption that the statewide uniform guideline formula amount is the correct amount of child support to be ordered. ( 4057.) The presumption can be rebutted by showing that application of the formula 'would be unjust or inappropriate in the particular case . . . .' (Ibid.) . . . "If the court determines that the statewide uniform guideline formula amount would be unjust or inappropriate in a particular case, the court must state 'in writing or on the record' the reasons why the amount of support ordered differs from the guideline amount. ( 4056, subd. (a)(2).) The court must also state in writing or on the record the amount of support that would have been ordered under the guideline formula. ( 4056, subd. (a)(1) . . . .) The court's order is reviewed for an abuse of discretion." (County of Stanislaus v. Gibbs (1997) 59 Cal. App. 4th 1417, 1419-1420 69 Cal. Rptr. 2d 819.) Section 4055 sets forth the uniform guideline formula for child support determinations. Section 4055 provides in relevant part: "(a) the statewide uniform guideline for determining child support is as follows: "CS = K HN - (H%) (TN). "(b)(1) the components of the formula are as follows: "(A) CS = child support amount. "(B) K = amount of both parents' income to be allocated for child support as set forth in paragraph (3). "(C) HN = high earner's net monthly disposable income. "(D) H% = approximate percentage of time that the high earner has or will have primary physical responsibility for the children compared to the other parent. . . . "(E) TN = total net monthly disposable income of both parties. "(2) to compute net disposable income, see Section 4059. "(3) K (amount of both parents' income allocated for child support) equals one plus H% (if H% is less than or equal to 50 percent) or two minus H% (if H% is greater than 50 percent) times the following fraction: