These strokes are written in 3 groups of 3 notes. If these paradiddles are being played in triplets in bars of 4/4 they will shift over 3 quarters in the 4/4. Light gray means mf. A bold note means accent. The bold B means Bass Drum. For a video example I refer to HERE
Of course you can play these paradiddles in 16th notes but realize that it are 9 notes. In sixteenth notes the paradiddle will shift in a strange way.