The following is the official documentation for the String function LEFT:

Explanation
One way to view a measure in Tableau Desktop is to split it into bins. You can think of bins as buckets based on a range of values. For example, say you have a measure that represents age. Instead of aggregating the measure to calculate the average age, you can bin the measure to define age groups: 0-5, 6-10, 11-15, and so on. Then you can count the number of people in each age group.
Create a calculated field for variable bin size
Step 1
Select Analysis > Create Calculated Field.
Step 2
In the Calculated Field dialog box, complete the following steps:

Since Sales is a measure, it can easily be depicted via size.
To drill down and change the level of detail, Country is the correct choice since it will contain STATE. We can then depict the various states by different shapes such as circle, square etc.
Finally, the Profit can be depicted via a color! Eg - Red for poor and green for excellent profits!

Explanation
When you connect to a new data source, Tableau assigns each field in the data source as dimension or measure in the Data pane, depending on the type of data the field contains. You use these fields to build views of your data.
Further,

Explanation
Follow the steps to get the correct answer : January 2018

* We are talking about dates, so use the Time series sheet as follows:
* Next, the following should be your view and clearly, January 2018 is the lowest point:

Read more about dates:
https://interworks.com/blog/rcurtis/2017/01/30/tableau-deep-dive-dates-introduction-dates/