My take? That’s clearly a STAMPED date. The “1” had more ink on it and was therefore slightly darker. Therefore, the scanner choose to bring that in as a black numeral vs gray.
Same thing on the anti-aliasing throughout the document.
Ah, good catch - its stamped.
For that reason the right-hand-most number might well have been applied with more force than the others (by a right-handed stamper) allowing the scanner to treat it differently.
It’s plausible, anyway. Looks like we simply can’t draw reliable conclusions from a document scanned with OCR. Show us a photo Bambi!