For example, I have 4 flux-reborn solar panels that generate 32 RF/t each. I connected these solar panels to an Energy Cell (Thermal Expansion) that is slowly recharging. The average rate should be 119 RF/t ¹ but the screen switchs each seconds between 116 RF/t and 122 RF/t or something like that.

¹ = My screen needs 9 RF/t : 2 energy modules and 1 clock module.
Also, there is no way to center the time from the clock module. You could also add a blank module that would acts like a text module without any text on it, only to make a space separation.

I can't fix the rate. Measuring RF/t is not accurate and will always fluctuate like that