我发现Portfolio_UsedMargin + Portfolio_CurrentCapital 不等于 Portfolio_CurrentEquity ，这是为什么？

//计算可用金额对应最大仓位（真实价格）

Numeric calcAvailableSize(Numeric price,Bool islong)

{

// 按合约成交金额比例计算保证金

if(mRate.ratioType == Enum_Rate_ByFillAmount)

{

// 账号金额保证金最大持仓

Numeric MRatio = IIF(islong, mRate.longMarginRatio,mRate.shortMarginRatio) ;

Commentary("!!!MRatio:"+Text(MRatio));

Integer pos_available = IntPart( (Portfolio_CurrentEquity - Portfolio_UsedMargin) / (ContractUnit * BigPointValue * price * MRatio) );

Commentary("!!!UsedMargin:"+Text(Portfolio_UsedMargin)+",CurrentCapital："+Text(Portfolio_CurrentCapital)+",Equity:"+Text(Portfolio_CurrentEquity)+",sum:"+Text(Portfolio_CurrentCapital + Portfolio_UsedMargin));

Commentary("!!!sum-roll:"+Text((Portfolio_CurrentCapital + Portfolio_UsedMargin)/Rollover));

return pos_available;

}

return 0;

}