4 beats means hold upto 4 count (1,2,3,4)
2 beats means hold up 2 count (1,2)
1 beat means upto once only (1)
1/2 beat means 1/2 beat of 1 beat (1/2 +1/2= 1 beat) or (1/8 of 4 beats)
1/4 beat means quarter of 1 beat ( 4 quarter notes =1 beat) or 1/16 of 4 beats)