GPVAL_TERM_XSIZE behavior?

[Allin C. <cot...@wf...>]

I'm seeing something that puzzles me. I create a plot using this 
term line:

set term pngcairo size 762,600

Now I'm interested in retrieving the size of the PNG (which the 
venerable xv tells me really is 762 x 600). Using gnuplot 5.0.6 I 
get

GPVAL_TERM_XSIZE = 15240
GPVAL_TERM_YSIZE = 12000
GPVAL_TERM_SCALE = 20

and on division by 20 I get the size back OK. But using 5.2.8 I get

GPVAL_TERM_XSIZE = 15220
GPVAL_TERM_YSIZE = 11980
GPVAL_TERM_SCALE = 20

giving 761 x 599 on division by 20.

Is this inadvertant or is there a reason for the difference?

Allin Cottrell