Native Deaf signers will usually sign 1 through 5 with their palm facing themselves and this is what we teach our students. However, you will see some people who sign numbers 1 - 5 with their palm facing forward. This is okay - never correct Deaf signers.
However, when you join numbers together, such as 35, the numbers should face forward. So room numbers, phone numbers, etc - are generally signed with the palm facing forward.
Also - please note that there are a few regional versions of 16 to 19. We show the most common one that is used in most areas in Canada. But you will most likely notice other variations for 16 - 19. Make sure to observe what local Deaf communities are using and mirror them.