  In the Letter, an interesting method is proposed to estimate size of narrow
emission lines regions (NLRs) of a Type-2 AGN SDSS J083823.91+490241.1 (=SDSS
J0838) at a redshift of 0.101, by comparing spectroscopic properties through
the SDSS fiber (MJD=51873) (diameter of 3 arcseconds) and through the eBOSS
fiber (MJD=55277) (diameter of 2 arcseconds). After subtractions of pPXF method
determined host galaxy contributions, the narrow emission lines of SDSS J0838
in the SDSS spectrum and in the eBOSS spectrum can be well measured by Gaussian
functions, leading more than 90\% of [O~{\sc iii}] emissions to be covered by
the eBOSS fiber with diameter of 2 arcseconds. Meanwhile, both none broad
emission components and none-variabilities of ZTF 3years-long g/r-band light
curves can be applied to confirm SDSS J0838 as a Type-2 AGN, indicating few
orientation effects on the projected NLRs size in SDSS J0838. Therefore, upper
limit about 1arcsecond (2250pc) of the NLRs size can be reasonably accepted in
SDSS J0838. Combining with the intrinsic reddening corrected [O~{\sc iii}] line
luminosity, the upper limit of NLRs size in SDSS J0838 well lies within the
99.9999\% confidence bands of the R-L empirical relation for NLRs in AGN.
