Improve description of 'Keep unused patterns' export option

src/routes/home/Export/ExportOptions.tsx

@@ -113,7 +113,7 @@ function ExportOptions({ disabled = false }: { disabled?: boolean }) {
             name="keepUnusedPatterns"
             title="Keep unused patterns"
             disabled={disabled}
-            helperText="Add unassigned group patterns containing notes or MIDI expression as extra Session rows. They will not be added to the Song Arrangement."
+            helperText="Add unassigned group patterns containing notes or MIDI expression as extra Session rows. Patterns with the same number share a row and are not added to the Song Arrangement."
           />
           <CheckboxField
             name="groupTracks"