If you set "Percentage" to 0 then it because very easy for the camera to trigger on motion. To set the most stringent conditions, i.e. least likely to trigger, set "Percentage" to 100 and "Sensitivity" to 0. This will require almost the entire area you selected to monitor to be considered "moving" and the changes will have to be severe, e.g. dark object in bright background or vice versa. See my other post in "Motion detection" for advice on setting these 2 parameters.
I suggest first determining the smallest size you wish to trigger, compute the "Percentage", and then adjust sensitivity until it works. Note that since we can only input integer percentages, it may be difficult to get exactly the number of boxes you desire - I usually round up/down depending on the sensitivity response.
BTW - if you don't see the boxes to which I am referring in "Motion Setting", then you need to make sure you are using Internet Explorer. The other browsers will not work in setting motion detection area (such a pity, especially if you are not on a Microsoft platform).