1995 - 993 DME/ECU Part Number Question

[MST0118]

Hi All -

I have a question about the part numbers for the ECU/DME relating to a Porsche 993 with drive block that might relate to manual or tiptronic transmissions, etc. The part numbers are:

993.618.124.03
993.618.124.04
993.618.124.05
993.618.124.06

It seems that most of these ECUs have a Bosch number of 0.261.203.675.

Here's my questions, what do the .03, .04, .05, and .06 at the end of the part numbers specifically represent for these ECUs?