Steps to reproduce:

• create/open a simple Qt Quick UI
• switch to Designer mode
• border size of the root Rectangle is displayed as 1 (although it's 0)
• drag a new smaller Rectangle onto the root Rectangle
• border size is again 1 (although it's 0)

• if you modify the value either by entering another number or by clicking on the spinner it's displayed as it should - so only the initial value should be corrected