7 lines (6 with data), 250 Bytes

m126a 0 128 0 8:05:00 24/12/1989
# Start time=08:05
# First beat=08:10:35.421
# <age-range>: 65-69, <sex>: Male, <medication>: None
# <RR-low-limit(sec)>: 0.492,  <RR-high-limit(sec)>: 1.14
# Note: recording with a timing signal, flutter-compensated