Height / Width of an iframe

So when I try to change the height and width of that item, the curve inside it ( which I want to change ) doesn't actually change but the border around it does. I'd like to have some help with it and thanks ^^

    <iframe style ="height: 450px; width:900px; position: relative; align-self: center; align-content: center;" src="https://thingspeak.com/channels/1270796/charts/1bgcolor=%23ffffff&color=%23d62020&dynamic=true&results=60&type=line&update=15"></iframe>