I think those compare the currently shown data vs that of a previous set of data, based on your configured date range.
So, as an example, if your Analytics is currently showing data within the past 30 days, it compares the currently shown data against the data from 31-60 days ago.
Total Unresolved Tickets: current reading is ‘9’, which is down 25%, so previous data sample would have been ‘12’
In Freshservice, the "delta figures" feature ddd 63, although not explicitly named, can be inferred to refer to tracking differences or changes in metrics over time. This is typically done by comparing data from two points to measure changes in key service desk performance indicators, such as ticket counts or resolution times.