The “Highest quality/resolution” can mean many things. It is far better if you specify exactly the parameters that you used when exporting the video.
Try comparing the original and the new version visually side by side. If you can’t see any lowering of quality when you study them you shouldn’t worry.
Also, the highest quality setting is 100%, but you should not usually use this as many video players cannot handle that - anything over 67% is overkill. See the following thread for some useful information: