"lbs" is not correct. lb means pound (weight, not currency). lb is the abbreviation for libra, which is Latin for pound. The plural of libra is librae, not libras. Therefore, if you wish to write a plural amount of pounds (weight) you should write 10 lb, or 25 lb., not 10 lbs or 25 lbs. A singular amount of pounds should be written as 1 lb.