[STAAD PRO] Ask : API code design parameter

Gents, 

today i'm working on pipe/tubular section in my model. to check the ratio in analysis, i'm using API code, but for non tubular section, i use AISC 9th Ed.

however, i have some question regarding API code. (i use STAAD Pro v8i SELECT 4 20.07.09.31)

in API design parameter :

1.  BEAM command

BEAM

1.0

Beam parameter:

0.0 = design only for end moments or those at locations specified by the SECTION command.

1.0 = calculate moments at twelfth points along the beam, and use the maximum Mz location for design.

2.0 = Same for BEAM 1.0, but additional check is made at each end.

when i use BEAM 2.0 ALL -> it shows ERROR.

PARAMETER 6
CODE API
BEAM 2 ALL
RATIO 1.33 ALL
LOAD LIST 4
CHECK CODE ALL
FINISH

why it says ERROR ? 
if i use BEAM 1.0 ALL,  what's the different between BEAM 1.0 in AISC 9th Ed ?


2. MAIN Command

MAIN

0.0

Design for slenderness.

1.0 = Main member

2.0 = Secondary member

could you explain to me what is main and secondary member means ? In API RP 2A-WSD code they say secondary member is stair/ladder , boatways, etc.

otherwise will be as primary member.

 

but i'm not really sure if this is the same just like STAAD do.

your explanation is highly appreciated.

Thank You all.