The number displayed as the maximum upload size in the Collabtive file upload dialog is pulled from php.ini
To increase the maximum upload-filesize you need to edit your php.ini configuration file .
You may need to ask your hosting provider how to edit php.ini.
Some hosting providers won't let you directly edit php.ini but will do it for you on request.
All filesize settings in PHP config need to be in this form: 128M.
You need to edit the following settings:
The maximum size of an uploaded file. You may need to increase this. Example: 128M
Sets max size of POST data allowed. Should be larger than upload_max_filesize. Example: 130M
Sets the amount of memory PHP may use. Example: 128M