Sometimes, translating Microsoft Excel or Microsoft Works spreadsheets with ClarisWorks results in file sizes greater than the original file. In one case, a 20K Excel file grew to 180K in ClarisWorks.
The most likely explanation is that an entire row or column has been formatted in Excel or Microsoft Works, which inserts formatting information in hundreds of cells. When ClarisWorks translates this spreadsheet, it must create a document with many more rows and columns than actually contain useful data, resulting in a larger file size since ClarisWorks stores this data differently than Excel and Microsoft Works.
If you find this to be the case with any of the spreadsheets you translate, select the cells in the original application which have data and copy and paste into a new spreadsheet in that application. Save the file and translate it into ClarisWorks. This will usually result in a file size that is even smaller than the original spreadsheet file.