Q:

Numbers in git HEAD

I am compiling Openembedded and at the beginning we can see this :
meta-python       = "HEAD:1efa5d623bc64659b57389e50be2568b1355d5f7"
meta-lxde         = "HEAD:9c1501dcb95a8601c8d1fad73c1fcae2886c0377"
meta-browser      = "HEAD:1edcce7791b4cee9a515c1f11b351753a4f8b12e"
meta-qt4          = "HEAD:2c7f8df9039be498f8a2232d1428adb7f4e5e800"
meta-qt5          = "HEAD:9aa870eecf6dc7a87678393bd55b97e21033ab48"
meta-freescale-distro = "HEAD:ae27e8a8a068b960d6c1219f50b2e8ccc97f0bea"
meta-toradex-demos = "HEAD:9fa810182cbb085554ad3a596db6dbf1fc9a0a73"
meta              = "HEAD:c8d96b10ee3bc2eae0fd269d2564286fd0bc82ed"
meta-pjproject    = "<unknown>:<unknown>"

The numbers are written in .git/HEAD of each folders. But according to this question it has to be like this : 
$ cat .git/HEAD
ref: refs/heads/master

Why is there strange numbers?

A:

Why is there strange numbers?

This is build system's way of informing what it is building.
Let's take a look at one of the lines
meta-python       = "HEAD:1efa5d623bc64659b57389e50be2568b1355d5f7"

When you triggered the build command, I guess bitbake <some-machine>, the build system works its way up to the function base_get_metadata_git_revision, which runs the git command git rev-parse HEAD, thus gets the tip SHA.
In your case, when you got this log your meta-openembedded tip commit was this one. 
Note, that meta-python is a subdir in the meta-openenbedded git, that's the reason you get meta-openembedded SHA for meta-python.

