If you want to apply conditional validation on 'Second Number' or 'Third Number', then you need to add 'First Number' input as '25'
{{userFormGroup.controls.firstNumber.errors.factor.message}}
To apply the validation of factor on 'Fourth Number' field, then enter the value '25' in 'First Number' textbox
Conditional Expression with type 'string'
{{userFormGroup.controls.thirdNumber.errors.factor.message}}
To apply the validation of factor on 'Fourth Number' field, then enter the value '25' in 'First Number' textbox
Conditional Expression with type 'function'
{{userFormGroup.controls.secondNumber.errors.factor.message}}