Percentage Problem with ISExec

[Prince4]

Guys another problem i'm facing right here A friend gave me fix for the Batch Execution that i needed for my inno Script and the good thing is that the Execution is working and the .bat also finishes its work, But i don't know why i'm facing this stupid problem :

//Setup-1.Rpk (4.75 GB) --> [8.37 GB]
				if not ShowChangeDiskWindow ('Please Locate Part 1 To Start Installing...', ExpandConstant('{src}'),'Setup-1.Rpk') then break;
				if not ISArcExtract ( 0, 50, ExpandConstant('{src}\Setup-1.Rpk'), ExpandConstant('{app}'), '', false, '{#PassWord}', ExpandConstant('{tmp}\ISDone_Params_ExTended.ini'), ExpandConstant('{app}'),False) then break;

        //function ISExec(CurComponent:Cardinal; PctOfTotal,SpecifiedProcessTime:double; ExeName,Parameters,TargetDir,OutputStr:AnsiString;Show:boolean):boolean; external 'ISExec@files:ISDone.dll stdcall delayload';
        if not ISExec ( 0, 0, 0, ExpandConstant('{app}\Rebuild.bat'), '', ExpandConstant('{app}'), 'My comments',false) then break;

        //Setup-2.Rpk (4.75 GB) --> [8.37 GB]
				if not ShowChangeDiskWindow ('Please Locate Part 2 To Continue Installation...', ExpandConstant('{src}'),'Setup-2.Rpk') then break;
				if not ISArcExtract ( 0, 50, ExpandConstant('{src}\Setup-2.Rpk'), ExpandConstant('{app}'), '', false, '{#PassWord}', ExpandConstant('{tmp}\ISDone_Params_ExTended.ini'), ExpandConstant('{app}'),False) then break;

Now you must note that the ISExec code doesn't have any Pct specified,
But no matter why does the Progress instantly jumps to 100% from 45%

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