Number of groups:

Each group includes a certain number of data items. (Often
all the groups have the same number of items, but that is not required.)
What is the size (i.e., the number of items) of largest group? (maximum: 99)

Size of largest group:

There is no harm is over estimating the group size: blanks will be ignored. You do need to correctly enter the number of groups.

For ANOVA with a error-bar plot click here.