Male plants never have berries. The berries are the fruits of the plant and contain seeds. They grow from an ovule which is the female part of the plant. The male flowers have stamens which produce pollen and therefore can never grow berries.
Most flowers have both female and male parts in the same flower but sometimes they form on different plants, like Pernettya.
If the plant you saw had 'smaller berries' I wonder if those could actually be the buds of the male flowers that have not opened yet ?

as Hywel says the male wont have berries. what you are seeing could well be flower buds or the remains of the male flowers. Though usually they just drop off so I think next years flowers the most likely.

Hello. I have an update on this plant. I contacted the garden centres plant manager as my plant didn't have a care label just the sticker saying male plant. It turns out that this is a hermaphrodite ( both male and female) called Bells Seedling. The male berries are sterile in that they don't have seeds whereas the female ( my existing plant) berries have seeds. ( I have checked my plants and this is true), so planting them near each other should result in berries next winter. Here's hoping.
Happy Christmas one and all.

Thanks for the update Barbarak. unusual to have both male and female flowers.

Thanks for letting us know. It is very interesting but strange ...