I would say that is absolutely fine and is just about the right ratio, he‘s not only learning to be left on his own but also that not every day is exactly the same and that the times vary, so that if you do find that you occasionally have to leave him for an hour or so longer, it shouldn’t be a problem.
At the end of the day, its all about the quality of the time you‘re together, many people are at home all day every day with their dogs but the dogs can still be bored and lonely if no one interacts with them.
As long as Trigger doesn’t appear to be stressed in any way and there are no signs of barking, scratching, toileting in the house, I wouldn‘t worry. Generally the accepted maximum length of time they can be left is around 6 hours but obviously that can vary depending on the individual dog, you know Trigger best and you obviously include him in family life so I‘m sure you‘d know if he wasn‘t happy.
Well done for working on the transition though!!! ! SO many people don’t and the result, post lockdown, is and awful lot of unhappy and stressed dogs (one of whom lives at the back of us, is left outside all day and is so stressed it breaks my heart 😢)