PSMATCH2: one to one matching

I would like to get a matched sample by running the code below

Code:

psmatch2 y x1 x2, logit common

Is this the correct code to do a one to one matching using logit regression on common support?

If so, why do I get the below results.

Code:

count if _nn == 1

This gives more than 2000 observations.

Code:

count if _nn == 0

This gives more than 7000 observations.

Shouldn't they output the same number of observations if it is a one to one matching?

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