A lot will depend on the code in between, but a Boolean true value is conventionally represented as the integer value -1. It all depends on how you are handling the value before it gets persisted. Some code would be useful if you need further help.
EDIT: The code added shows you are relying on an implicit cast from Boolean to integer, resulting in this -1 value. In VB, depending on the version, you could use Iif(checkbox1.Checked, 1, 0)
or If(checkbox1.Checked, 1, 0)
. Alternatively, keep the value as a Boolean, and save to the appropriate underlying DBMS data type if there is one - for example, in SQL Server, this would be a bit
data type.