I read this as making the author's point somewhat sarcastically. I understand that the point is being made in one of two ways ( the maximum/optimistic way and the minimum/cynical way). The right way will become clearer from your context:

1. If you've given the company all the value you can for the day and have done all you can for the day, you are free to go. Yes, IN THEORY you could sit at your desk and by doing so come up with new, additional or better ways of doing things but the reality is that a person has only so many productive hours in a day and nothing of value is to be gained by staying the additional two hours past your internal clock's quitting time.

--If you've given the company the minimum value required to satisfy your commitment for the day and have done all you contractually or legally owe for the day. you should be free to go. Yes, IN THEORY you could sit at your desk and by doing so come up with new, additional or better ways of doing things but why woul dyou do that if you are only being paid to do what is in your job description? You don't gain anything more by staying the additional two hours past the time when you've satisfied the minimum requirements of your job.

Because your sentence sounds like it is a compliment about a company rather than a criticism, I suspect that my first meaning may be the one that fits, but only you can tell for sure!