Quite easy....

a ton of cooling and heating is 12,000 BTUs.

So for a 3 ton heat pump model, full BTUs would be 36 K minimum both in cooling and heating.

One should always look at the matching AHRI number to get the number of BTUs for a HP both in cooling and heating.

While not naming a particular brand, there are models that fail to give you full BTUs. I have seen a large haircut close to 10% on the heating size on some models. This can be a big deal. Buyer does not always get what he thinks he is.

IMO