Reproduction steps:
1. Open the user's attached project "Sandbox.zip"
2. Select "Square" from the Project window
3. Open Sprite Editor from the Inspector window and observe the border
4. Select "Square (Converted to Single Mode)" from the Project window
5. Open Sprite Editor from the Inspector window and observe the border

Expected result: L, R, T, B border values of both Sprites are 0
Actual result: L, R, T, B border values of "Square" are 0; L, R, T, B border values of "Square (Converted to Single Mode)" are 4

Reproducible with: 2019.4.36f1, 2020.3.28f1, 2021.2.11f1, 2022.1.0b6, 2022.2.0a3

Notes:
1. The border values don't change when changing the Sprite Mode of any other Sprite from "Create/2D/Sprites"
2. 2019.4.36f1 doesn't have "Create/2D/Sprites", issue reproduced by downgrading the project
3. Not reproducible with Square from "Create/Sprite" on 2019.4.36f1