If there is a symbol then it is likely not very commonly known. So in any case you have to explain it somewhere what the symbol means and it might confuse your readers.
However, if you have to plot multiple tables then it might be useful to abbreviate notation.
A possible way could be to use markers like an asterix $^*$ or other symbol that indicates a footnote.
For instance a table could look like
**Current actual figure
2020* 3235 (2887)
*projected figure (current actual figure)
I often see tables with only the projected figure (and some marker and footnote to explain it is projected) but I admire your attempt to also show the current figure. An alternative could be
Year Number of statisticians going crazy
*projected figure based on current 2887 statisticians