Note that there are 12 people with below-average arm spans. Most of them (10/12, or 83.3%) are also below average in height. Also, there are 12 people with above-average arm spans. Most of them (11/12, or 91.7%) are also above average in height.
Note that the proportions and percentages are counted for the groups of arm spans only. The proportion 2/12 in the upper left corner of the table means that two out of 12 people with below-average arm spans also have above-average heights.
It is important to note that the proportions across each row may not add up to 1. When we look at column proportions, we divide the values in the contingency table by the total number of values in the column, rather than in the row. In this example, there are 13 values in the first row, but there are 12 values in the column; therefore, we're looking at proportions of 12 rather than 13.
Percentages are equivalent to proportions but can be more descriptive for interpreting some results.
Since 91.7% of the people with above-average arm spans are also above average in height, and 83.3% of the people with below-average arm spans are also below average in height, this indicates a strong positive association between arm span and height. Note that in this study, we're using the word "strong" in a subjective way; we have not defined a specific cut-off point for a "strong" versus a "not strong" association.