StringUtil.java

import android.text.SpannableString;
import android.text.style.RelativeSizeSpan;

public class StringUtil {

    public static SpannableString spannableString (String value, int number){
        SpannableString s = new SpannableString(value);
        s.setSpan(new RelativeSizeSpan(0.7f), s.length() - number, s.length(), 0);
        return s;
    }
}