This option is provided so that you may select the appropriate 5250 model. This will be used to set the screen size, adjust the screen attribute handling, and to provide terminal identification to the host machine where appropriate. All of the models have screens with 24 rows of 80 columns, except the 3477-x models which have 27 rows of 132 columns:
5555-C01 is 24 x 80 DBCS (Double-Byte Character Set) display 5555-B01 is 24 x 80 DBCS monochrome display 3477-FC is 27 x 132 display 3477-FG is 27 x 132 monochrome display 3180-2 is 27 x 132 monochrome display 3179-2 is 24 x 80 display 3196-A1 is 24 x 80 monochrome display 5292-2 is 24 x 80 display 5291-1 is 24 x 80 monochrome display 5251-11 is 24 x 80 monochrome display 3812-1 is printer 5553-B01 is DBCS printer
If you select a printer type, you will probably also need to specify the printer device name to connect to.