How big does a follicle need to be to be considered mature for ovulation?

Patient's question:

Detailed medical condition and consultation purpose: How big should an follicle be considered mature to be able to release the first egg? Additional question: Hello, when having an ultrasound, the doctor usually writes something like 1.51.8, 0.91.1. What should I look at? How many follicles are being released like this? Second additional question: Hello, when having an ultrasound, the doctor usually writes something like 1.51.8cm, 0.91.1cm. What should I look at? How many follicles are being released like this? Can the experts help me answer more detailedly? Third additional question: June

Doctor's answer:

The size at which an egg follicle matures and releases varies from person to person. Some may release it when it reaches 15mm, while others need it to grow to 25mm. Specific ultrasound monitoring of ovulation during a cycle will provide clarity. Generally, there is one or more follicles of varying sizes. However, usually only one mature egg is released each month, with the others atrophying or being absorbed by the body. Under normal circumstances, an egg follicle measuring 20mm or larger is generally considered mature and ready to be released.