Why are poeple being charged £2.10 on my journey?

On the First Glasgow website, the following information regarding single fares is displayed

http://m.firstgroup.com/ukbus/glasgow/tickets/ticket-type/tickets-single_fare

Ideal for the occasional bus passenger

We’ve introduced a flat fare structure within the Glasgow city area and have individual single fares in operation across the rest of our network in the Dumbarton, Kirkintilloch, Cumbernauld and Lanarkshire areas.

In Glasgow you’ll pay either of two single flat fares:

Glasgow Single Fares
Longer hop
(anywhere within the city zones) £1.85
Single fares in Dumbarton, Kirkintilloch, Cumbernauld and Lanarkshire are based on the distance travelled.

For children we’re introducing a straight flat single fare of only 75p for journeys of any length in any area.

Glasgow City Map – PDF – (373 KB)
Terms and conditions

Single fares are valid for a single bus journey at any time of the day
This ticket is non-refundable as a result of, but not limited to, the failure of services to operate.

Now can anybody explain why on service X8, that passengers are being charged £2.10 for a single trip when the website clearly states a ‘Longer Hop’ anywhere in the city zones is £1.85. Pollok & Silverburn are both well within the city zone.

There seems to be a few passengers being caught out with this.

As far as I know, other express routes such as the X81 from Robroyston to Glasgow charge the £1.85 fare