Can you explain this sentence more descriptive: "System automatically brings extra quantity like 35, 41,48 etc"
From your story I would assume it is because of a rounding profile, but it could be anything else as you were not even able to post a screenshot that correlates with your own words.
Isn't it logical to show a screenshot from a PR with a quantity of 5 and a second screenshot from a PO with a quantity of 35 where you also make sure that the PR number could be seen in the same screen to validate that the PO belongs to this PR only.