Alt text for pictures

Hi,

I got a serious problem about alt text of pictures. I uploaded all pics with title and alt text correctly in the media folder. I uploaded them in the pages. Once I have published the website, I noticed that if I try to save one of the picture, it has a different alt text. here an example: http://touchsystems.co.uk/top-business-management-software-tools/

last picture should have as alt text “smiling-team”, but if I try to save it, it shows “smiling-team-354×354.png”. Why?