How to ignore the "Default value"?

[ccdr]

I'm using data logger suite modbus TCP query/response parser to fetch data from modbus TCP server.
The data occupy 2 registers and are parsed as 32-bit float.
So I set "Registers to read" to 2 and "Count" to 1.
But I can not get valid data upon every request. The next query following the valid data query is an invalid one with the exact data I set in "Default value" field.
How could this happen?
In what condition, the "Default value" is used as parsed data?
If this is inevitable, how could I ignore such "Default value" avoiding the parser variable to log this nonsense value?
Thanks.

[Arthur Grasin]

Hello,

The program uses the default value in case if the program cannot extract the specified value from a response (a response does not have necessary number of bytes)

You cannot omit a response item if it does not exist in a response.