Very little info to go on.
On PA form PA-40 Line:
11 is your taxable amount.
12. Your PA tax
13. Total withheld
14. Credit from last year not refunded.
18.Total credits and withholdings.
24 Total payments and credits.
Apparently your credits were 686 short and shows on line 26 Tax due.
The earlier numbers would be clues why it is 686.
