By default, your table will SUM vertically. This means that for any single-select question, the SUM of the rows in a single column will add to 100% (or 99% to 101% due to rounding error). However, do note that for multi-select questions, the sum of the rows will not add up to 100%, as respondents can select more than one response.
In the screenshot below you can see that we have a root question, which is "Do you watch movies regularly (at home or at the cinema)?". And 79% of the respondents said yes, while 21% said no. And we've added a cross-break for age groups, which shows how the fallout of the responses changes across different age groups.
A helpful tip for reading the column breaks is to start with a specific response option in the root column (i.e. Overall), and then compare the column breaks to the same response option/cell. Here's an example:
Among the Overall sample, 79% of respondents watch movies regularly, and this increases to 87% among those aged 16 to 24. Among those aged 45 to 54, the share of those who watch movies regularly decreases to 76%.
Changing the table SUM direction
In some cases, you may want to change the direction that the table SUMS the data. Since we know that tables in Canvas SUM vertically by default when you click on the button labeled SUM this will change the direction so that the data now SUMs horizontally.
Changing the table SUM direction has significant implications for how you interpret the table. Instead of starting with the column, you should now start with the response option (i.e. Yes or No in the screenshot above), and then look at the distribution across the column breaks. Here's an example:
Among those who are regular move watchers (79%), 18% are aged 16 to 24, while 31% are aged 25 to 34.