Hi,
The issue lies in the SVG, it automatically scales to 100%, please modify this line in the SVG:
<svg width="100%" height="100%"
to
<svg width="64" height="64"
for the 64 pixel one. You can re-use this image for the other sizes as well. There is no need to add multiple SVGs. The only thing to be aware of is that it should be a fixed size SVG.