7 lines (6 with data), 251 Bytes

m248a 0 128 0 9:40:00 02/02/1991
# Start time=09:40
# First beat=09:48:19.867
# <age-range>: 50-54, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.468,  <RR-high-limit(sec)>: 1.156
# Note: recording with a timing signal, flutter-compensated