The problem is that font size is shrunk by adjustsFontSizeToFitWidth = true, but it does not adjust the lineHeight automatically. It remains to be for original font size that is 50.
By default, the text is aligned to its baseline. you can adjust it with baselineAdjustment property.
In your case, you should set it to UIBaselineAdjustment.alignCenters.
valueLabel.baselineAdjustment = .alignCenters