7 lines (6 with data), 247 Bytes

m257a 0 128 0 8:00:00 05/08/1989
# Start time=08:00
# First beat=08:17:17.835
# <age-range>: 60-64, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.507,  <RR-high-limit(sec)>: 1.054
# Note: reel-to-reel recording, not flutter-compensated