So, mother has agreed on getting a Blue tongue skink

However, i have a small problem. The animal itself looks healthy even though two are being kept together. No toes missing, good colour, food every day.....

BUT! Its just 22 cm long or so, and he said it was nearly a year old......so this northern BTS is quite, or very, tiny. Will he be able to grow to normal size of about 60 cm with proper food, or will he stay a midget? D:

should i buy it? D: Its well taken care of and looked calm when handled....but i dont want another midget pet. ( my female turtle is VERY much smaller than average, even with plenty of varied food u__u )