How does the density of a water in a tank and the density of a water in a glass can be same density since water's density is 1

and it's formula is mass/volume

since the tank's water is more than as a volume that of the glass and also more than as a mass that of a glass

Just because there is more mass in a certain substance doesn't mean it's density will change. In this case, water, will not change density simply because there is more of it. I. e the ocean. The bottom of the ocean may have more pressure to it because of the weight of the water above it but if you were to take a cup of it and take it to the surface it wouldn't sink.

because there is more mass in a citizen substanse does not mean is density will change