Can you adjust the step count for someone who has a limp. The person is doing a lot of walking for not many steps being counted. Are the steps counted by what your hand does or your feet stepping ???

Steps are counted by rhythmic arm swings.

I just climbed a couple flights of stairs and walked around the warehouse.  My watch was in the front pouch pocket of my hoodie.  Both the steps and stairs were counted correctly.  It's more complicated than "rhythmic arm swings". 

I said about arm swings, because this is where the watch is usually worn, but the watch doesn't care if it swings on your arm or in your pocket.

You can flail your arms around and it will show as steps taken. 

Attach it to a dog's collar (or tail if brave) and what your step count blow past the daily goal. 

The watch has a sensor called an accelerometer which measures directional movements in all directions. When walking, there is a rhythmic swing and upward lift when our calf muscles push the ground and accelerate our body. The watch senses this rhythm and starts counting steps.

Try walking 30 steps and pausing to see what the watch counted. Was it accurate? If not, try putting the watch on the other arm and repeating. If the limp is on only one side, this switching of wrists may improve accuracy.

I hope this helps.

A custom stride length might be a viable solution. 

A custom stride length will have absolutely no effect on step count.