These guys know that, in general, you do not do as much when you are working from home as you do in the office.
There are some people who are the exceptions. But they are just that, exceptions. Certain jobs can be done from home, on-line customer service for example. The calls are fed to you and you have to put your station on hold for a potty break. That time is measured as is how much time you spend on calls. So the company has a metric to measure your work and so do you.
But for a lot of jobs this kind of metric does not exist.
They can see how long you are on the company website but are you actually working?
It’s easy-are your projects being completed? Your customers happy? Have you created or improved something that brings quantifiable value?