As you type, the editor searches the file for a match. The pop-up shows how many matches are in the current file. To move through the matches while the Find box is still active, press Tab or F3 to move to the next match and Shift+Tab or Shift+F3 to move to the previous match.
If you press Ctrl+F a second time, SEGGER Embedded Studio for ARM pops up the standard Find dialog to search the file. If you wish to bring up the Find dialog without pressing Ctrl+F twice, choose Search > Find.