How to set decimal points on Polkadot.js.org account balances for parachain

Question

Every time when I start my parachain, I see Bob, Charlie, Dave,... etc and each of them has 1.1529 MUNIT on Polkadot.js.org's Accounts -> Accounts -> My Account page. But how does Polkadot.js.org know my parachain's decimal places?

What does the M mean? like 1 Million with 6 zeros?

After sending 100000000000000000 with 17 zeros as the value from one account to another, finally that shows up on that above Accounts page as 0.1MUNIT. Assume M means 6 zeros, then 12 = 18 - 6... The Accounts page shows balance with 12 decimal places... where did that come from?

After some digging, I found those inside the chain_spec.rs

pub fn development_config() ...
    properties.insert("tokenDecimals".into(), 12.into());

pub fn local_testnet_config() ...
    properties.insert("tokenDecimals".into(), 12.into());

So the 12 dp must come from there... right? That is how Polkadot.js.org set its decimal places in the Accounts page. Right?

https://polkadot.js.org/apps/?rpc=ws%3A%2F%2Flocalhost%3A8844#

Answer 1

Yes the tokenDecimals can be hardcoded in the chain_spec.rs file (like you have shown) or they can be configured in the chain spec of the chain. For example, in Polkadot's chain spec you will see the following:

"properties": {
    "ss58Format": 0,
    "tokenDecimals": 10,
    "tokenSymbol": "DOT"
  },

• https://raw.githubusercontent.com/paritytech/polkadot/master/node/service/chain-specs/polkadot.json