If you want to apply conditional validation on 'Practical Exam Marks' or 'Passing Marks', then Obtained Marks must be less than '35'
{{userFormGroup.controls.obtainedMarks.errors.lessThan.message}}
Other Activity Marks less than to Obtained marks
{{userFormGroup.controls.otherActivityMarks.errors.lessThan.message}}
If you want to apply conditional validation on 'Passing Marks' then you need to add 'Obtained Marks' field less than '35'.
Conditional Expression with type 'string'
{{userFormGroup.controls.passingMarks.errors.lessThan.message}}
Shows custom message
{{userFormGroup.controls.otherMarks.errors.lessThan.message}}