Pop-up window underutilised with scaling <1

[alxmtvv]

With scaling of 1 everything's fine, with scaling <1 "useful" area of pop-up window decreases, seemingly corresponding exactly to the scaling value. Attached is an example of 0.75 scaling - only approximately 75% of the window is used, the rest is blank, even though there's more lines to show. With 0.5 scaling used area decreases to about half of the window.