Its a typical requirement but will try to provide solution. There is no need to increase the size of the group section just Try Below given way.
1. Insert 11 group sections.
2. Place the data field in 1st group section.
3. In the remaining 10 group sections place a line and write the supress condition for individual group section on the number of records retrived. For e.g if 5 records are retrived then 5 group sections with lines should get displayed and remaining sections with lines should get supressed, If 10 records are retrived then all 10 sections should get supressed.
Note: This is not a tested code.