Question: 

Fluke has posted adjustment procedures for the Fluke 1503 and 1507. 
There is possibly some confusion regarding the initial steps C-1 through C-10 mentioned in Table 10 on page 24, where is stated:
connection must take place between +: COM and -: A gnd (remote test probe pin).

In order for this to be connected correctly, how should I connect  A gnd via the input terminals ?

Answer: 

The + output of the calibrator can be connect to COM of the 1503/1507. 

The - output of the calibrator can be connected to the following pins of the remote probe connection, J4 and/or J6.
These are the A gnd connections of the 1503/1507. 

 See this part of the schematic : 

         View on Bottom view of circuit-board :

When looking at the 150x inputs from a users perspective, the two inner pins of the remote-test probe connections can be used as the A gnd connections.
See picture below :