Should Self-Assessments be Scored? (not Graded)
The purpose for student self-assessment is formative in nature and is typically to encourage reflection and monitoring of learning.  There are several papers that highlight effective practises in formative assessment in higher education, the foremost being Sadler[1] and Nicol[2].  

Central to both of these is students knowing what constitutes good performance.  Depending upon the nature of your questions, an overall met/not met summary of expectations presented to the student can provide them with a measure of performance. It is simply an indicator that they still have to practise and work on some aspects to achieve a desired performance level. 

Sadler, D. R. (1989). "Formative assessment and the design of instructional systems." Instructional Science 18: 119-144. 

Nicol, D. and D. Macfarlane-Dick (2006). "Formative Assessment and self-regulated
learning: a model and seven principles of good feedback practice." Studies in Higher Education 31(No.2): 199-218.