In the same way as encountering your first books isn’t the same as learning to read, counting to one hundred isn’t the same as learning to count.
In the same way as singing the alphabet song isn't the same as recognising the letters, counting to one hundred isn’t the same as learning to count. Before a child can begin to understand numbers and what they mean, they need to become familiar with number words, and the sequences they come in.
Try to make counting fun by using songs and nursery rhymes to introduce numbers. Most of us know ‘one, two, three, four, five, once I caught a fish alive’ but you can make up your own tunes or get them to sing the numbers along to a favourite song and see where you can get to. Once counting to 100 is secure, try counting in tens. As well as reinforcing the order of the decades, counting in 10s is the beginning of multiplication and the first step to mastering those pesky times tables!