Adjusting offset for vertical-supporting CJK with symbol-placement: line

[cs09g]

Question

CJK fonts can be displayed in vertical but others like number are still displays in horizontal. It's okay but the space between number and the text right next to the number is narrow(depending on fonts, it may look they are stick together). So, I changed the value of 5 to 8.
(value 5 is what @ChrisLoer experimentally selected: detail's in here)
Seems like the value might be depending on the font, so I'm not sure the offset can be fixed as 5.

Screenshot

when the value is 5: unbalanced space beside the number

when the value is 8: