Number sequence reset to 1

Dear all, 

I face an issue in voucher number sequence.

When i create a transaction in general ledger the voucher number suddenly reset to A-13000001. I check the sequence, The next sequence should be A-13000028. The sequence already set to the continuos.

I've already check the voucher sequence before and there is no transaction at all regarding this voucher number.

Does any one know why the sequence suddenly reset to 1 ?

Thanks in advance

Regards

Rudy