|nOffset||(Long) Specifies the position of read value in the data block.
The read value must be inside the data block. The item is read either whole or not read at all.
>= 0 - Index (in bytes, zero-based index) in the data block.
-4 - The internal automatic position is used (see the AutoOffset property). It points behind the last read or written value.
This operation shifts the internal automatic position behind the read/written value.
If the items are read/written one by one then it is not necessary to define the position manually, but it is better to use this automated positioning.