New sunspot produces intense shortwave radio bursts

A new sunspot appears in the southern hemisphere of the sun, and it looks like a sign of a new solar cycle 25. The sunspot AR2758 even produced one of the first solar radio bursts.

How do we know that this sunspot belongs to the solar cycle 25? The southern sunspots from the old solar cycle 24 have a polarity of – / +. This sunspot is the opposite: + / -.