word choice - "This is actually true" vs. [sic]

I often find myself in need of a short expression, to emphasize that what I just wrote (not quoted) is actually true. In cases of paradoxes or illogical truths for instance, like The Monty Hall Problem.

It is not always possible to explain that something is actually true, nor does it look pretty to constantly add "(This is actually the truth, despite it seeming to be incorrect)" at the end of what might just be a 2-digit number in a small table-cell.

Apart from adding an asterix, or footnote, with an explanation at the bottom of the page, is there a [sic]-like alternative? An abbreviation that simply says "This is actually true/the correct value despite looking incorrect/seeming illogical"?

---

Assuming none exist, the only way to get a new phrase or abbreviation into the language/dictionary is to start using it... With that in mind, just for laughs, what would you prefer as a new expression?:

cbt - "counterintuitive but true"

sya - "surprising yet accurate"

tis - "this is so" (I think we'd best avoid "this is true"...)

Or perhaps cor for "correct"? Could create some confusion as it is already used as an expression in british, but I kinda like that idea.