Having problem adding people to groups

When I try and add people to groups if I look up a person it pops up a window with 9 names out of possible 13 people. I cant find a way to scroll the list. I tried to narrow the list by searching on the last name (i.e. burns) but the name Zachary is still at the bottom and I can't scroll down to pick it - so I cant add him to a group. It also changes the format of the list when I search to include pictures - which is sort of cool - but changes how many I can see in the list.