ESS is the Effective Sample Size:

#Effective sample size
ESS <- function(w) {
  weights <- weights * s.weights
  n <- matrix(0, ncol=2, nrow=6, dimnames = list(c("All (ESS)", "All", "Matched (ESS)","Matched", "Unmatched","Discarded"),...

The treatment weight of 1 is why both the "unweighted" and ESS are 3127. If you had another question please clarify it.

These resources may help:

https://www.jstatsoft.org/article/view/v042i08

https://gking.harvard.edu/cem

https://github.com/kosukeimai/MatchIt/

ESS is the Effective Sample Size:

#Effective sample size
ESS <- function(w) {
  weights <- weights * s.weights
  n <- matrix(0, ncol=2, nrow=6, 
              dimnames = list(c("All (ESS)", "All", 
              "Matched (ESS)","Matched", "Unmatched","Discarded"),...

The treatment weight of 1 is why both the "unweighted" and ESS are 3127. If you had another question please clarify it.

These resources may help:

https://www.jstatsoft.org/article/view/v042i08

https://gking.harvard.edu/cem

https://github.com/kosukeimai/MatchIt/