how do PSSE calculate VAR without specific command

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i met a problem when using the software psse. i wrote the wrong command psspy.branchpandqchannel([100,24,26,30,38],r"""1""",["",""]) instead psspy.branchpandqchannel([100,-1,-1,30,38],r"""1""",["",""]) the difference is 24 vs -1, which i have learned that is the VAR index. and 24 in my case has been used. then I confused what kind of VAR have been done without our addtional command. i run a case and found there are 29 var address have been used. please tell me typical usage. i knew that IEEET1 excite model need KE be a var.

by the way, what happened to my wrong command? don't the program just clean the no.24 address var value and calculate again?

i am not a English-speaking man, forgive my rough expression. Appreciate your help, regard