I can only assume that you have 2 dimensions in "Columns" section in your Pivot Table.
Judging by "+" or rather "-" icon on one of your columns you probably have not checked "Fully Expanded" under "Appearance-->Presentation".
This is the way Qlik Sense automatically presents levels-->Bold indicates that you can expand. Once checked "Always expanded", everything becomes visible, and bold font disappears.
Unfortunately we do not have control over this settings and it comes set like this "out of the box"
hope this helps