Some negative numbers read incorrectly

```
What steps will reproduce the problem?
1. Read a row from an XLS file containing a number.
2. Echo one of the cells.

What is the expected output? What do you see instead?
The number is for example -6504.34. php-excel-reader echoes it as 10731120.61.
Some numbers are read correctly but they are smaller (-444.3 is read correct).
The formatting of the numbers is General.

I tried reading it with PHPExcel and it read these numbers correctly. But I
can't use that library cause the sheet contains 50k+ rows and php-excel-reader
is small and fast and efficient.

Can I get a quick fix or something? This is really important.

```

Original issue reported on code.google.com by `endar...@gmail.com` on 17 Jul 2011 at 8:39

Start by reproducing the report in php-excel-reader with an XLS row containing -6504.34 and compare it with the correctly read -444.3 value. Trace the XLS number-reading path and verify that negative General-format values are returned unchanged rather than converted to a large positive number.

Written by the indexing model from the issue text.