Some links for you to read on the subject of dosing :
As you can see, the protocols for starting to take NDT are not all the same. If you are relatively healthy (other than thyroid issues) - no heart problems, for example - then I would follow the protocol in the first link. If you are elderly or suffering severe health issues I would go with the more conservative protocols in the 2nd or 3rd link.
Some comments :
You will often see people referring to "grains" when talking about dosage of NDT. Depending on brand this is usually either 60mg or 65mg of NDT. So you have been prescribed 1 grain of NDT per day.
60mg Erfa is roughly equivalent to 75mcg - 100mcg T4, depending on who you read. Personally, I believe it is closer to 75mcg rather than 100mcg. So even when you take all your Erfa you may be quite under-dosed.
Different people do well on different brands of NDT, so if Erfa doesn't suit you don't despair, there are others to try.
Don't forget as well, that there are other options open to you - a combination of T4 and T3, or T3 only, or any other combo of NDT, levo, and T3.