7 lines (6 with data), 252 Bytes

m253a 0 128 0 13:30:00 21/06/1989
# Start time=13:30
# First beat=13:30:00.695
# <age-range>: 45-49, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.492,  <RR-high-limit(sec)>: 1.414
# Note: recording with a timing signal, flutter-compensated