About the usage of Total data years, Total trading years, Total data Months, Total trading Months

In the process of using SQX to develop and test strategies, I gradually understand that using  standardized indicators (mean annual indicators, monthly indicators.) as much as possible will make the work simpler and more efficient. So i usually use Avg. trades per year, Ret/DD ratio per year and so on. I know that in most cases, we test strategy and data start from on January 1 of a certain year. But in some special cases, I may import custom data(such as Non-US futures.), and the starting time of its data may be any day of the year, and I don't want to waste any data. Please see the situation shown in the attachment. Suppose I have to choose a very specific time range segment,Let me take crude oil as an example.data range is 2013/7/10-2022/10/13,That's a total of nine years, three months and three days.

1. According to code, avg. trades per year = # of trads/total data years, Is this calculation appropriate? However, Ret/dd ratio per year(custom metric)=Ret/DD ratio/total trading years.
2. What is the difference between total data and total trading? Does it mean rounding? One is small and the other is big?
3. Because there are always some test cases, the start time of the data is not necessarily January 1 at the beginning of the year, and the end time of the data is not necessarily December 31 at the end of the year. Obviously, the calculation error of monthly metric is very small. But for all standardized annualized performence metric, such as avg. trades per year, ret/dd ratio per year and so on. Considering better universality of the calculation formula.Whether it should be calculated according to the actual  days and months of sample data converted into an annual number?  In fact, I think it's accurate enough to annualize it on a monthly basis.