If you want to apply conditional validation of less than equal to validation on obtained marks or practical exam marks then Total Marks must be 100.
{{userForm.controls?.totalMarks?.errors?.lessThanEqualTo.message}}
If you want to apply conditional validation of less than equal to validation on 'Obtained Marks' then then Total Marks must be 100.
Conditional Expression with type 'string'
{{userForm.controls?.practicalExamMarks?.errors?.lessThanEqualTo.message}}