ModBus on SL/HL/W - Mislabelling?

[FatMax]

I believe there is some text confusing my understanding with a manufacturers modes documentation. 

When they refer to Holding registers(#4), my device tells me that is actually number 3. Which is correct?

   

   

[admin]

Both are correct
Numbering in your doc refers to "traditional numbering standard", while RTU read test uses Modbus function number. For some historical reason address numbering and function numbers for registers are swapped. Keep in mind that actual registers are numbered from 0, not from 1 as specified in your doc.