Just parenthesis without values indicate the mere existence of a built-in, retractable diffuser (usually paired up with a bouncer plate).
Values in parenthesis additionally indicate the widest focal length and the resulting guide number when using the diffuser.
Zoom (28) 35 - 80 mm + GN (16) 26 - 34 m
Widest focal length covered with the flash is 35mm at a max. guide number of 26m. Using the diffuser the covered angle will increase to 28mm at a max. guide number of 16m.
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