Is Cure Resin suppose to leave a dent if you push it too hard?

So i use Art Resin and weight it by 2:1 Ratio…i mixed it throughly for more than 6 minute at least and stir it slowly to avoid micro-bubbles as best as i can,i stopped mixing it after all the streaks are gone… So long story short i finished the painting inside the Resin and sealed with the final layer. Did the same thing and just left it for weeks..i was playing around with it until i noticed that if i pushed the cured resin too hard it will leave a small dent but then will go back to its original shape again… i find it surprisingly weird.. i thought it was suppose to be like glass… i read somewhere that Resin is only 95% solid ? is this the reason why ?