Good morning, the child weighs 40 kg and has received a Zinnat 250 dose every 12 hours of 5 ml Isn't that enough for strep throat?

Regarding dosage, follow the information given to you by your doctor.

Please note that the dose depends on the severity of the infection, the susceptibility of the microorganism causing the infection, the patient's condition, age and weight. Only a doctor can therefore make decisions on this topic because he knows the health status of his patient.
Knowledge about age and body weight is insufficient. Too low a dose may be ineffective and instead of curing, it will only cause the bacteria to become resistant to this antibiotic. Too high a dose can be harmful and cause increased side effects.

I am attaching materials and information that may be useful:

https://www.gdziepolek.pl/tematy/jak-rozpoznac-i-leczyc-angine

https://www.gdziepolek.pl/tematy/fakty-i-mity-o-antybiotykach