### TRIAL:ACTUAL_START_FIELD

The first frame number in the C3D file is stored in two
unsigned 16-bit values to form a 32-bit value. The
first unsigned 16-bit integer is the least significant word while the second
unsigned 16-bit integer is the most significant word therefore the first frame
number is calculated as:

First frame number = ACTUAL_START_FIELD[1] + ACTUAL_START_FIELD[2]*65535