28 days compared to nothing (CityLab seems to be US based) is infinitive percent more :)
The median number of vacation days for most categories of workers is about 15 (https://www.bls.gov/ncs/ebs/benefits/2017/ownership/private/...).
I'm actually surprised that many part time employees are given paid time off at all.
And there's the rub: it's expected over here.
28 days, though 8 of them can be the standard public holidays, leaving 20. It's pro rata for part time employees, and often given as cash to people on temporary contracts.