Entering something like that would be Sat[2,4]: 09:00-16:00 given the opening day would be the even saturdays.

BUT as your photo is different from what's shown on their website where it just says "Saturdays" - albeit the COVID-19-info page that still speaks about Tier 2 measures and a potential lockdown (and thus is at least 2 years old) - I have written them an email asking about the current state.