docs: update README.md [skip ci]

add information about PIN number MIN and MAX length

README.md

@@ -248,7 +248,7 @@ touch:
 
 <img width="708" alt="image" src="https://github.com/user-attachments/assets/571bc5f9-1c80-49a1-b1c7-61cb7974d8b2">
 
-2. Open this [website](https://www.devglan.com/online-tools/hmac-sha256-online) to hash your pin number. Add you pin number as plain text, in the first input. You must use numbers only because the UI doesn't support letters or symbols, and it must contain at least 6 digits.
+2. Open this [website](https://www.devglan.com/online-tools/hmac-sha256-online) to hash your pin number. Add you pin number as plain text, in the first input. You must use numbers only because the UI doesn't support letters or symbols, and it must contain at least 6 digits and no more than 20 digits.
 
 3. Copy the generated hash. It must be 64 characters long.
 
@@ -276,10 +276,10 @@ security:
 
 <img width="708" alt="image" src="https://github.com/user-attachments/assets/571bc5f9-1c80-49a1-b1c7-61cb7974d8b2">
 
-2. Open a terminal and run the following comand to hash your pin number. Don't forget to substitute `"YOUR_6_DIGITS_PIN_NUMBER"` and `"YOUR_32_CHARACTERS_LONG_SECRET"`. The PIN number must contain only digits, and be at least 6 digits long.
+2. Open a terminal and run the following comand to hash your pin number. Don't forget to substitute `"YOUR_PIN_NUMBER"` and `"YOUR_32_CHARACTERS_LONG_SECRET"`. The PIN must consist only of digits and must be between 6 and 20 digits in length.
 
 ```bash
-echo -n "YOUR_6_DIGITS_PIN_NUMBER" | openssl dgst -sha256 -hmac "YOUR_32_CHARACTERS_LONG_SECRET" | awk '{print $2}'
+echo -n "YOUR_PIN_NUMBER" | openssl dgst -sha256 -hmac "YOUR_32_CHARACTERS_LONG_SECRET" | awk '{print $2}'
 ```
 
 <img width="988" alt="image" src="https://github.com/user-attachments/assets/503a01de-0a4f-4bf8-95a3-d5ed660bfcee">