Positive selection population identification using xpehh

I am using Rehh package for identification of positively selected genes from our study. I am using the following script but confused with right reference.

ies2xpehh(
scan_pop1,
scan_pop2,
popname1 = NA,
popname2 = NA,
min_nhaplo = NA,
standardize = TRUE,
include_freq = FALSE,
p.side = NA,
p.adjust.method = “none”,
verbose = TRUE
)

Here, which population is positively selected xpehh score. Popname1 or popname2?

Please share your experience.