how to create a rule for at least one number and lower char

[Snoopy]

basically (for fast hashes) a built in logic to decline pw candidates like this would slow down the whole process of cracking, therefore you might be better using just a mask with 7 all lowercase combined with a handcrafted ruleset which switches 1-x letters to upper and replace 1-x with a digit

see example rules toggle* and built up your own ruleset