How does width and height in itemSize calculate?

[fishefam]

It does not seem that the values I set to these properties are in px. The size of items are not what I expect when they render on screen.

[cuire]

Grid uses gap to calculate size of item. This behavior reflects the CSS grid.
https://svelte.dev/repl/78f82f3461a940ee93cb774a187f5cbc?version=4.1.1