For the Opening Balance measure, note that all values for January 2017 are blank. This is because there is no ending value for the month previous to January 2017. For February 2017, note that the value of the Opening Value measure is 155.00. In the data, 155.00 is the value of January 31, 2017. Also, note the value for January 2018 dates. The value is 136.92. Note that in the data, this is the value (rounded up to two decimals) of December 31, 2017. Thus, the OPENINGBALANCEMONTH function essentially lists the final value as computed by the expression specified in the first parameter, in this case, SUM([Value]), for the previous month.
The Closing Balance measure utilizes the CLOSINGBALANCEMONTH function. This works similarly to the OPENINGBALANCEMONTH function except that it lists the final value for the month as computed by the expression specified in the first parameter, in this case, SUM([Value]).
The Month to Date measure utilizes the TOTALMTD function. At the day level, you can see that this measure is summing up the current day as well as any previous days in the month since we have specified the computational expression to use SUM([Value). In the Matrix visualization, the value of 1,710.00 is displayed for the Month to Date measure. This value of 1,710.00 corresponds to the Month to Date measure value for the date January 31, 2017. Thus, we can see that the TOTALMTD function computes the value of the specified expression for all days in the current month in context that are on or before the current date in context.
The Previous Month measure also uses the TOTALMTD function with the same calculation expression, SUM([Value]), but, for the dates, specifies the PREVIOUSMONTH function. January 2017 dates are blank because there is no previous month's data. However, the February dates all read 1,710.00, which is the value for Month to Date for January 31, 2017. Hence, using the PREVIOUSMONTH function as the dates clause causes all dates within the previous month, and only those dates, to be included in the calculation of the specified expression. This may or may not be what you intended! For example, what you might have intended was for this measure in February to show the total for the same number of days in January. If this was indeed the intention, then we could have used the DAX function, PARALLELPERIOD, to achieve this.
The Year to Date measure uses the TOTALYTD function. This function works in an identical manner to the TOTALMTD function, except at the year granularity. Similarly, Previous Year makes use of the PREVIOUSYEAR function, which works identically to the PREVIOUSMONTH function except at the year level of granularity.