I know how an isotropic antenna works. I work in the certification business and I keep seeing 0 dBi gain antennas. I have an antenna 0 dBi gain (Whip antenna) with Beamwidth 360 horizontal and 45 vertical. Is this possible?

I thought it was:
Beamwidth:
H, 360
V, 90
Gain = 3 dBi

Beamwidth:
H, 360
V, 360
Gain = 0 dBi