The Read from file command File and Folder Interaction | EPF Docs does take an optional at startPos parameter, but that is the start position based on bytes of data, not lines. Try this code:
put the number of lines of File "C:\TestPlant\logs\em.log" into myLineCount
put 7 into LogCount
put lines LogCount..myLineCount of File "C:\TestPlant\logs\em.log"