7 lines (6 with data), 252 Bytes

m252a 0 128 0 15:36:00 06/07/1991
# Start time=15:36
# First beat=15:41:17.312
# <age-range>: 45-49, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.617,  <RR-high-limit(sec)>: 1.125
# Note: recording with a timing signal, flutter-compensated