Volume Permissions Unexpected User on Windows

Hello everyone

I'm trying to understand how the Ownership of Volumes works on Windows for Docker Container.

I'm using the following Dockerfile as a test

FROM centos:7

MAINTAINER Lovely Sausage

RUN echo "root:root" | chpasswd

# DUMMY MYSQL

RUN \

adduser mysql && \

mkdir -p /mysql

# DUMMY POSTGRESQL

RUN \

adduser postgres && \

mkdir -p /postgresql

When I run it using the following command

docker run -d -v //c/mysql:/mysql -v //c/postgresql:/postgresql --name centos7_vol1 centos7_vol

I can see that the folders have ownership as follows

drwxrwxrwx 1 mysql ftp 0 Nov 21 11:43 mysql

drwxrwxrwx 1 mysql ftp 0 Nov 21 11:43 postgresql

I don't understand why especially because if I change the Dockerfile so that the DUMMY POSTGRESQL part comes before the DUMMY MYSQL part then the ownership is as follows

drwxrwxrwx 1 postgres ftp 0 Nov 21 11:43 mysql

drwxrwxrwx 1 postgres ftp 0 Nov 21 11:43 postgresql

Where are these permissions being set?