Entity parameters keep changing

I'm trying to draw a centerpoint arc slot but whenever I change one parameter another one changes automatically. I had this problem with other entities also but somehow attained the desired parameters by constantly changing the parameters manually until they wouldn't change automatically anymore. I got lucky, but my lucks run out. Can this be turned off?

This is how I want the slot:

radius = 35mm

angle = 45deg

thickness = 10 mm

Thanks.