Skim Matrix Variable Explaination

[HuyLeDinhGia]

Hi ActivitySim Dev Team,
I'm currently developing a model for Melbourne and want to implement ActivitySim. However, I do not clearly understand the description in the document. I have some questions as below:

1. Regarding the Skim matrix, can you help me explain what are these parameters and correct me if I'm wrong:
   IVT - In-vehicle time, if this is train or bus so it is the time in bus, train
   IWAIT - Initial wait time, the time the transporter waits at the station for the bus, train
   XWAIT - Transfer wait time, the transfer time between trips
   WACC - Walk access time, the time from their origin to the station
   WAUX - Auxiliary walk time, the time the transporter travels from the current station to the next station
   WEGR - Walk egress time, the travel time from the last station to the destination
   TOTIVT - Total in-vehicle time, if the transporter uses a car, it is the sum of in-car time and in-train/bus time
   KEYIVT - Transit submode in-vehicle time, I don't understand this, can you explain more?

2. In the example_estimation project, there are some modes such as EXP, LFR, and COM, and I don't want to use this but I can't find the disable/enable variable for these. Do I need to update the expression myself?

3. Is the example_estimation project enough for a general and simple model?

Regards,
Huy