Provided {$MACRO} stores numeric value (positive integer to be precise) one can use the following construction in calculated item expression:

{$MACRO}{$MACRO}

Implicit concatenation is the last thing to expect from numeric values in mathematical expression. Implied multiplication would be more appropriate since it is a commonly accepted mathematical notation. In trigger expressions such constructions are not allowed, this can be a way to go too.

Depending on the desired behaviour this issue should be treated as frontend or server bug.