This was noted several times in this topic: you don't need to wait any time to give +karma after you accidentally gave -karma. You can do it immediately and the problem will be solved the same time. 
Oh, I did not notice this. Thanks for this information, as I thought if we gave either negative or positive karma, we couldn't give another either positive or negative for 10 hours. That's why I never tried, as I made this mistake maybe one or two times, as I was using my mobile, and I mistakenly clicked on the negative karma button instead of the positive one.
And about the karma being more faster and not taking long to give same user karma not taking that 10 hours long then if the time is adjust then many user will definitely abuse the karma and it will really be a bad way to the forum and that ain’t proper. I don’t see anything wrong with the karma activity, I guess the user that missed your karma which was unfair you can definitely give the user whom deserves it now since you have recall. I don’t know maybe you get my point.
Jokers just pointed out that if we gave negative karma to anyone, we can quickly give positive karma and the matter wil be closed, so if we want to give positive karma again, for that I think we have to wait 10 hours, which is a good time, and as I said, I liked this system. Speaking of spam and admins and mods being busy, that's not a thing, they are very active whenever someone is abusing karma, they deal it ASAP I have seen.