TOTP not match If we pass totpSize = 6 and step = 60

This code result match with Google Authenticator

```
var base32Bytes = Base32Encoding.ToBytes(key);
var totp = new Totp(base32Bytes);
var totpCode = totp.ComputeTotp();
```

This code result not match with Google Authenticator

```
var base32Bytes = Base32Encoding.ToBytes(key);
var totp = new Totp(base32Bytes, totpSize: 6, step: 60);
var totpCode = totp.ComputeTotp();
```
Google Authenticator URI example

`var uriString = new OtpUri(OtpType.Totp, key, "myemail@yahoo.com", "Test Not Working", digits: 6, period: 60).ToString();`

Start by running the two Totp snippets and comparing their results with the Google Authenticator URI created by OtpUri using digits: 6 and period: 60. Read the Totp constructor parameters and OtpUri serialization to trace how totpSize and step are represented. Done means the generated six-digit code matches Google Authenticator for the 60-second period.

Written by the indexing model from the issue text.