What does PB mean?

[astrina]

<p>There’s a question-mark bubble at the top of the column. Click it.</p>

<p><a href=“http://registrar.ucsd.edu/StudentLink/instr_codes.html[/url]”>http://registrar.ucsd.edu/StudentLink/instr_codes.html&lt;/a&gt;&lt;/p&gt;