A hint

From the OBi Device Admin Guide
"x - a wild card digit that matches any digit from 0-9. x is CASE SENSITIVE"
"Starting with release 1.2, the following elements are added:
....
@ – A wildcard character that matches any alphanumeric character except #
...."
(BTW Releases 1.2 onwards also include:
" x? – matches 0 or 1 x
@? – matches 0 or 1 @"
which gives scope to halve the number of "|" separated items in the black list.)