This Wikipedia page contains information about the star Spica in the rightmost table. A small snapshot of this table is below.
In this table, the absolute magnitude is given as
−3.55 (−3.5/−1.5). Instead of seeing the value and error given as
value ± error, I am thinking the error is given as it is because of absolute magnitude is given on a logarithmic scale (as opposed to linear scale). But I am not quite sure how to interpret this as an error reading. How does one interpret this reading?