單子的總量不符

本人將特大單、大單、中單、小單分別分開作成畫面，其買進與賣出總量竟不相等，原因如何？

{指標數值定義："大戶單=特大單+大單資料為分鐘統計張數"

//舉例來說，買盤大戶買賣比是 買進大戶金額 / (買進大戶金額 + 賣出大戶金額) * 100，要計算過去15分鐘的資訊的話就會是:

支援商品：台(股票)}

variable:XD(0),YD(0),ZD(0);

input:tTime(090000),eTime(133500); setinputname(2,"起算時間%");

//if barfreq <> "Min" then return;

value1 = GetField("買進特大單量");

value2 = GetField("賣出特大單量");

value3 = GetField("買進大單量");

value4 = GetField("賣出大單量");

value5 = GetField("買進中單量");

value6 = GetField("賣出中單量");

value7 = GetField("買進小單量");

value8 = GetField("賣出小單量");

value9 = (value1 + value2 + value4 + value5 + value7 + value8);

value13 = value1 + value3 + value5 + value7;

value14 = value2 + value4 + value6 +value8;

value15 = value13 -value14;

if value9 <> 0 then value10 = 100*value7/(value9) 

else value10 = 0;

if value9 <> 0 then value11 = 100*value8/(value9)

else value11 = 0;

value12 = (value7 - value8);

XD = XD[1] + value12;

plot1(value12,"小單");

plot2(XD,"累小");

if tTime < time and time < eTime then plot2(XD,"累小");

plot3(value10,"買小比");

plot4(value11,"買小比");

plot5(value13,"買單");

plot6(value14,"賣單");

plot7(value15,"和");

最後總和並未等於0，即買進與賣出不等，原因為何？我無法理解，請給予指導，謝謝