for my son, we do 6 puffs, if no improvement, up to A&E we go.
They give him 10 back to back and see how he gets on. It makes him very shakey and gives him a blinding headache, but its done under supervision.
So you can have another 6 puffs (total 10) but if theres no improvement, please get to hospital or walk in centre as quickly as you can. Call 999 if necessary.
My paramedic friend says this weather has made every second shout an asthmatic.