Can anyone explain this???

ali (Student CA CPT ) (130 Points)

22 March 2014  
Is there any similarity between these two errors : 1) The total of the purchase returns book has been overcast by Rs 50. 2) Goods purchased for Rs 550 from anil have entered in the purchases books as for Rs 515. and what kind of errors do they belong to. ( TWO SIDED ERRORS or ONE SIDED ERRORS ) and how to rectify these errors when there is suspense account and when there is no suspense account.