You have the form
[A +B;
C - D]
The bottom row of that is a binary operation between two scalar values, and gives a scalar result. The bottom row is scalar.
The top row is two scalar expressions, one of which happens to be preceeded by unary plus. Just like [3 -5] is the pair (3, -5), [3 +5] is the pair (3,+5). The top row is a vector of two values.
To solve the problem you can either code A+B with no space, or you can code A + B with space after the +
