Please explain differences between R and r


I received my dissertation back with comments from the dean. He flagged the following text and added the following comments:

"Researcher should review for accurate nomenclature and revise as needed. Specifically, “R” is traditionally used when discussing multiple regression analysis as opposed to simple bivariate correlations “r”, moreover, the value reported .349 is the value of r squared. Researcher should revise as necessary."

This is the text.

p. 98 The regression line is drawn to correspond to the regression analysis completed. R-square is the percent of the dependent variable that is explained by the independent variables. The R2 value is .349 suggesting the line represents 34.9% of the data.
Am I correct that the comment suggests where I used the text R2 should be "r-squared" instead? Also, does someone have a better text or article explaining if there is a difference between "r-squared" and "R2" and "r2" ... If I recall correctly, SPSS put R2 as a line in the scatterplot and calculated the value. Should this have been r2?

As always, thank you for the help!