Calc exports the selected range to image with additional wrong padding

Hi,
I try to use the file → export → png with the selection and copy → paste as a png.
It will gives the png with some additional padding on the right and bottom.
The padding seems to be affected by the size of selection.
How can I get rid of these padding without cutting them by myself?

LibreOffice version: 7.6.2.1 on Windows 10
Step:

  1. select A1 to F30
  2. set the background or the border (just for visualization)
  3. copy
  4. paste as a png (check the right and buttom)

right is the png (pink is just background to show padding). also the size seems not to be the same as the original selection.

https://bugs.documentfoundation.org/show_bug.cgi?id=134842