I just bought a cheap tankless HWH, need help with supply line

I just bought a cheap FASTAR tankless HWH. I need help with installing proper supply lines. The water inlet and outlet and the natural gas inlet lines are all supposed to be 1/2 inch steel pipes according to the user manual. I took a ruler and measured the pipes' outside diameter which is 0.8 inches and the inside diameter which is 0.6 inches. I'm not a plumber. All 3 connectors are male and have threads on the outside. Can 1/2 inch pipe actually have 0.6 inch inside diameter?
BTW, Marey sells a smaller model with almost identical connectors and according to their video the supply inlets in the unit are 1/2 inch male FIP connectors. I thought FIP stands for Female Iron Pipe. What is a male FIP? The video URL is below watch the water inlet supply line connector part towards the beginning.
[ame="https://www.youtube.com/watch?v=g5-WBNUBCx0&t=473s"]https://www.youtube.com/watch?v=g5-WBNUBCx0&t=473s[/ame]

Video?? I just see A BLACK BLANK picture.

MIP male iron pipe
FIP female iron pipe

get a get a 1/ 2fitting and try it
.

Try this video...

[ame]https://www.youtube.com/watch?v=g5-WBNUBCx0[/ame]

Never mess with gas

Mr_David said:

Video?? I just see A BLACK BLANK picture.

MIP male iron pipe
FIP female iron pipe

get a get a 1/ 2fitting and try it
.

Click to expand...

and then you have a slip coupling
that has not made up its mind whether it is fip or mip

I believe .06 is 3/8''

I'm still baffled by using Teflon tape on a gasket-ed fitting. The guy slipped a rubber ring into the barb fitting then tightened it with his fingers all but the last 1/2 turn. What is the TT for? That's the same as using TT on a Union.

Thanks for the comments. I learned a lot from this project. That video has a few incorrect information, such as the "male FIP". All FIPS are female by definition.
The tankless water heater installation was completed 3 days ago. The only issue I have is that I did not tighten the water inlet coupling too much because there were no ways to attach and use a backup wrench (see video) on the water inlet or outlet. I did not want to tighten the coupling so hard that it broke the water inlet pipe. I used pipe joint compound instead of Teflon tape because people told me pipe compound is better. Now, it drips slowly from the water inlet. The drip frequency slowed down a lot over the last 3 days. Now, it drips once every 5 minutes instead of every 5 seconds 3 days ago. Will the slow leak/dripping completely go away after a few days? Others told me to tighten the coupling until the dripping stops. Is it OK to take a risk and tighten the coupling without using a backup wrench and with the supply line already attached to it? The inlet pipe is brass and round - no way to use a wrench - I may have to use pliers.

I don't see why pliers or channel locks wouldn't work.