encodder overflow with motorware lab12b

hello,

my motor max speed is 5000rpm, when motor speed up to 5000rpm, gMotorVars.SpeedQEP_krpm changed to -5.0.

and motor maintained at 5000 rpm, meanwhile, i could not control motor speed by  gMotorVars.SpeedRef_krpm.

system became uncontrolable but hardware did not explosion.

my encoder lines is 16384(USER_MOTOR_ENCODER_LINES = 16384)

and USER_MOTOR_MAX_SPEED_KRPM = 5.0

is there have any overflow or some other problem?

ps:I could not find any real effect on USER_MOTOR_MAX_SPEED_KRPM.