Arabic numbers (characters with bidi property "an") should be left to
right, just as European numbers ((characters with bidi property "en"). 
Currently Arabic numbers are made right to left:

\setupdirections[bidi=global]

\starttext
12345\par
١٢٣٤٥
\stoptext

Both line should have the same digits order.

I think "d == "an"" in core-spa.lua line 1075 should be moved to line
1071 (I tested it and it does fix this issue for me).

-- 
 Khaled Hosny
 Arabic localizer and member of Arabeyes.org team