7 lines (6 with data), 252 Bytes

m263a 0 128 0 14:41:00 13/01/1991
# Start time=14:41
# First beat=14:47:13.226
# <age-range>: 70-74, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.578,  <RR-high-limit(sec)>: 0.968
# Note: recording with a timing signal, flutter-compensated