Question about decimals for erc-20 tokens

[Playboi]

I don't think i'm fully understanding something here

For example, lets take the MAKER token
https://etherscan.io/token/0x9f8f72aa9304c8b593d555f12ef6589cc3a579a2

It says the total supply is: 1,000,000 MAKER and it has 18 decimals.

Did the developer enter it in with the following value:

Initial Supply: 1,000,000,000,000,000,000,000,000
Decimals: 18

----
Similarly, for QASH
https://etherscan.io/token/0x618e75ac90b12c6049ba3b27f5d5f8651b0037f6

The total supply is 1,000,000,000
Decimals: 6

so in remix.ethereum.org, did the developer enter

1,000,000,000,000,000
Decimals: 6

----

Im just trying to understand the significance of decimals,