A cover letter as a motivation letter
A lot of candidates don’t send a cover letter claiming that no one will read it. If you want people to read your cover letter, do not send it as an attachment.
The cover letter should be the message itself. This way, colleagues at the HR need to read it. Of course, we need to be careful about the length of the cover letter. Normally, it should not be longer than a half A/4 page, and you should also keep this limit if you send your cover letter as an e-mail.
Numbers in your cover letter
You can, of course, write about anything you want, but however well-structured your cover letter is, it needs to be supported with numbers to be plausible. Do not hide the results you achieved, express them in figures. When writing a cover letter as an accountant you can describe the budget gaps you filled in, as a sales manager you can talk about the revenue increase you achieved, or if you work in production, you can mention the developments you implemented. Of course, always keep in mind full respect of business secrets.
Don’t forget that this is the only chance to make a “defence speech” to give reason for your application and sell yourself.