@uncooked Welcome to the forum!
What you’re seeing is normal. The character class selectors only specify what characters are included when the generator randomly chooses each character for the password.
With your selection, there are a total of 62 possible characters to choose from, 10 of which are numbers, and 52 of which are not numbers. Therefore, if selecting a character at random from this pool, the probability of selecting a non-numeric character is 52/62 = 84%. If generating a 14-character password, then the probability that none of the chosen characters are numeric will be (52/62)14 = 9%. If generating a 26-character password, then the probability that none of the chosen characters are numeric will be (52/62)26 = 1%.
If you happen to get a password that includes no numbers, and if having at least one number is important to you, then you can simply generate a new password.
I don’t know why you’re using an insecure webpage (full of trackers) to generate any passwords, though. If you instead use the secure generator tools that are available inside the Bitwarden Password Manager apps and browser extensions, then you also have the option to specify the minimum quantity of numerical characters that should appear in each generated password.