7 lines (6 with data), 252 Bytes

m100a 0 128 0 16:45:00 28/06/1989
# Start time=16:45
# First beat=17:28:33.781
# <age-range>: 70-74, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.476,  <RR-high-limit(sec)>: 0.757
# Note: recording with a timing signal, flutter-compensated