how can we get weekdays to show human-readable labels? ask around, some in the class have succeeded, it involves casting the chart to JS code and modifying the tick formatting of the relevant visual encoding if you want to do percentages, like parts of the total you need to compute those on the data first, can be a good exercise too

you are using aggregation on Y encoding correctly, this good! minor thing: could have added some left margin too to fit the numbers, there is a button for that as well

could be also interesting to decouple names from sizes into separate columns and look for patterns in each answering your question about data dimensionality... here is an example how the same data can be represented in different dimensionalities: [date, namesize, state] vs [date, name, size, state], the second one would give you better opportunities for analysis