What Tags store

When an image gets tag, the tag data will store the data the user tagged, and NaN for all the other tags of the question set. For example lets say the user tags an image as follows

{
    "isSnow":true,
    "isRock":true,
    "somethingElse":"maybeSo"
}

And lets say the total number of question is 5, wit the other two being isWater and size, then in the database and in export the data will be as such

{
    "isSnow":true,
    "isRock":true,
    "somethingElse":"maybeSo"
    "isWater":"NaN",
    "size":"NaN"
}