What are `widthDp` and `heightDp` as a `@Preview` parameter?

【My environment】

* Android Studio Arctic Fox | 2020.3.1 Patch3 build on October 1, 2021
* Gradle: 7.0.2
* AGP: 7.0.3
* androidx.compose.ui:ui-tooling-preview:1.0.1

Here is my code.

```
@Preview(
    showBackground = true,
    widthDp = 200,
    heightDp = 200,
)
@Composable
fun DefaultPreview() {
    Box(modifier = Modifier.size(100.dp).background(Color.Red))
}

```

And preview shows below.  

[![enter image description here](https://i.stack.imgur.com/k7sTa.png)](https://i.stack.imgur.com/k7sTa.png)

But I expected below.  

[![enter image description here](https://i.stack.imgur.com/RFqzN.png)](https://i.stack.imgur.com/RFqzN.png)

It seems that the box size is larger than I expected.
Does anyone explain that?