Hi Pat,
The groupings are based on the pulse of the current time signature, so when you are using 4/4, eighth notes should be in groups of 4 if they start on beat 1 or 3. In 3/4 they will be in groups of 2 starting on beats 1, 2, and 3, and in 6/8 they will be in groups of 3 starting on beats 1 and 4. We may add the ability to do custom grouping in the future.
Alex