“i was sat” means to sit, you were sitting / badia brand tears in the box kitchen

my mum used to always give me a row for saying ‘i was just sat there when….’ ’no,’ she would say, ‘you were sitting. earlier you sat down, then you were sitting. sat is the action,’ and i would say, ‘ok anyway so i was just sat there and then the doorbell rang so i just ignored it. and that’s why i didn’t pay the window cleaner.’