Minimum wage is 1.405. Hours per week is 38, there are 4,5 weeks in a month. I think the typical number of hours is 162.
No. There are 52 weeks in the year, five working days per week, so 260 working days per year. From that subtract 26 days' holiday (234). Then there are 12 days which are national holidays, let's say nine of which are on working days (225). And then the woman probably has 1.5 children and thus 2 'children days' per child per year (222 days). That makes 18.5 working days per month. Multiply that by seven hours and 45 minutes and one gets 143 hours per month.
Minimum wage is 1.405.
Isn't minimum wage now 1,500zl?
A supermarket cashier in a soft labour market like Szczecin would not earn more than about 10% above the minumum.
So she's on, by your guess, 1,650zl per month and working, as shown above, 143 hours per month. That gives an hourly rate of 11.54zl, which is pretty much double what the article claims.