SD card formatting using space

Hello,

Ok so I have a gopro that has an 8gb sd card inserted. The sd card only had 1gb free so I deleted all the files on finder on my iMac. This did nothing so I did the standard formatting and it restored it to 7.48gb. Although, I didn't think this was the full storage space so I formatted it again. It then showed that I only had 6.37gb free!! Please help. I want to get this space back and don't know how. Also I am doing this via the camera plugged in through USB, not directly through an sd card slot because my 2009 iMac doesn't have one, I'm not sure if this makes a difference?

When you deleted the files did you empty the trash?
Can you do the format with the camera? Would probably work better than using the Mac.

Always use the built-in format function of the camera you are using to format the cards it uses.

link

The video is in english...

The camera is not a genuine gopro and does not have this feature of formatting on the camera.

is there any way to regain the space? i Have checked to make sure it isn't in an unused partition. I just cannot find a way to get it back to 8GB or close to. Thanks for replies so far

ok so i used a dowloaded sd formatter and it said the sd card was not compatible. then i tried it again a few hours later and it wouldnt even show it was there. then i re-inserted it clicked refresh a couple times and it showed up and as 7.42GB so before i did anything i tried to open it in computer which said it needed formatting, so i did it using the sd formatter and it reduced it to 7.41GB but im happy with that.