Heartrate Question

I had an ultrasound at 8w1d, and the heartrate was 166. I had a peace of mind private ultrasound today with a company, and the heartrate was only 158 at 9w6d. Everything I'm reading online says that the heartrate should be at 175 by this point, and that the range is between 155-195 is normal. I know 158 is still technically in the safe range, but it's on the low end of the safe range. Also, the lowness wasn't because the baby was sleeping because we some it dancing around on the screen. After 2 miscarriages I have awful pregnancy anxiety, so I overanalyze every little thing. Is this heartrate concerning, especially since it's lower than 2 weeks ago, when it should be higher at this point?