First of all, you should your program in debug and check the contents of the table and the values. Then search via SE16 and see if these values exist.
Databases attached to SAP are relational. There's no concept of order. Your SQL simply brings back the first 10 records found in the table. So you may get different results that way.
A few tips:
1) Why prefix your field symbols with FS? The fact that they're in angle brackets is sufficient. Concentrate instead on giving them meaningful names. <fst_bsis_line> is a bad name. As said, the fs is pointless. Something like <bsis_lines> - SAP advise now against the use of prefixes like t_)
2) In your select name the fields you're selecting. It's more explicit, which is better programming. It may even perform better.
3) Since the program goes straight into selection, the clears/unassigns are not necessary. With sensible use of local variables and modularisation, you don't need to ensure that variables are empty before putting a value in.