"Livello" is Italian for layer. In my UK English version of AI, it appears as <g id="Layer_2" data-name="Layer 2">
However the tag <g id>
is only a group id, not a layer as such. So, you can just remove the tag if you want. Obviously you mustn't forget to also remove the relevant </g>
tag
Here's an example showing two rectangles, deleting the <g id="Layer_2" data name="Layer 2"
, and renaming the other group IDs. I'm using Notepad++ for editing the XML.

Edit: After comments from the OP, and a little more research it would seem there is a better way to export an SVG rather than using Export Selection. Using Export As seems to give less quirky results, with no manual editing required.
Anyway, here's what I did
- Click Object > Artboards > Fit to Artwork Bounds.
This will rescale the artboard to fit the artwork.
- Click File > Export > Export As, choose SVG as the file format,
then hit Export
- The SVG export dialog will appear. Click OK

Here's the XML output without any manual editing. It's pretty clean, with no Illustrator weirdness.
<svg id="Layer_1" data-name="Layer 1" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 136 325">
<defs>
<style>.cls-1{fill:#bcbec0;stroke:#231f20;stroke-miterlimit:10;stroke-width:6px;}</style>
</defs>
<title>Untitled-1</title>
<rect class="cls-1" x="3" y="3" width="130" height="319"/>
</svg>
The difference between the viewbox and object dimensions is simply due to the size of the stroke. If there were no stroke, the viewbox and object dimensions would be identical. Also note that in the SVG export dialog you could set the Object IDs to "minimal" - which will get rid of the <SVG id="Layer>
nonsense, which is unnecessary.