Indian mathematicians (e.g., Brahmagupta in the 6th century) developed the idea of 0 as more than a placeholder.
In 1202, Fibonacci wrote "These are the nine figures of the Indians: 9 8 7 6 5 4 3 2 1. With these nine figures, and with this sign 0, which in Arabic is called zephyr, any number is written, as shown below."
Fibonacci seems to be saying that zero is not quite a number like the rest. But if he basing this off the Indians work from centuries before, why is this? Wasn't it well-developed by this point?
Thank you in advance!