If the range of your integer variable is from -300000 to 300000, you'll need to use int32 instead of int16.
This is taken from page 30 of the PI Server System Management Guide, available for download from the vCampus Library, under vCampus Library > vCampus PI Products Kit > Server Products > PI Server > PI Server System Management Guide.
As for status codes -253 and -307, you can look up the corresponding positive values in the System Digital State Set, using the Digital States plug-in of the PI System Management Tools:
-253 = Pt Created (this is the digital state of the event to indicate when the PI tag was created)
-307 = Bad (this indicates that the value retrieved from the source system is bad)