This is a crotchet rest. That is, the musician must pause for the same extent of time that a crotchet would take if played. A caprice is regarded as a quarter note, the brave being a whole note, and a semi-breve being half. However, the crochet is the kind of standard beat.
There are four crotchets in a bar, for instance, so that the most straightforward tune would have four crotchets in each bar, but that would be like a funeral.