Hi Sam,
First of all, many congratulations on taking on this poorly tortoise, and getting him seen to by a vet also.
It does sound like he had a terrible start in life, and he is lucky to have found a home with you. 7g is a lot to gain in a month, but then he was almost certainly underweight after such a long time in hibernation. Can you tell me what he weighed a month ago (that will tell me how big a percentage he has gained in the last month, as 7g on a large tortoise isn't so worrying as on a small tortoise). Also, if you can let us know his weight now, and his SCL (that is his length, measured in the prescribed way, which you can see how to do here
https://www.thetortoisetable.org.uk/tor ... Fi5VM3gq9s we can give you an idea of how his weight measures up to what we would expect.
We always say that we aim for an average weight gain of between 1g - 3 or 4g per month -- but that is just an average, and some months a tortoise will gain more than that an some months he will gain less. So 7g in one month isn't something to be too worried about, but if he consistently gains 7g or more each month, then you will have to monitor the quantity of food you give him.
Horsfields also present another problem in that they are incredibly greedy eaters. In the wild they live in areas where it is very cold in the winter (and they hibernate for a long time), and very hot in the summer (and they aestivate during the hottest periods). It's estimated that in the wild they are actually only awake for around three months a year, and during that time they eat for a very short period. So they are sort of programmed to eat as much as possible in a short time. That's fine in the wild, but in captivity where the temperatures are good and they are presented with lovely food every day, they can easily overeat, and they do need to be monitored. By the way, just because they are asleep for along time in the wild does not mean that they should be hibernated for 7 months in captivity! That is a terribly long time and I'm surprised that he survived it (three months is usually what we recommend).
I do think that your priority now should be to get this little fellow back to full health, and I don't think that gaining a bit over the average in the short term will do any lasting damage. Also, the type of food he eats is as important as the quantity. What are you feeding him, and is he getting a good calcium/vitamin D3 supplement (like Nutrobal) most days?
I think it was great of you to rescue this tortoise, and he is lucky to have found a home with you. You might already have one, but in case you don't, here is a link to a good care sheet for Horsfields:
https://www.tortoise-protection-group.o ... 014New.pdf
Nina