You have 4 GB RAM installed in a new server and EXSI says you have 3.88 GB so it prevents you from continuing the install. This is a workaround for that.

Based upon this article but I had to make a few changes to get the permissions to take: https://community.spiceworks.com/topic/411970-installing-esxi-5-5-with-4gb-ram-memory_size-error?page=1

1. Bootup VMware EXSI from live medium.
2. Wait for the "Welcome to VMWARE EXSI X.X.X installation" screen.
3. Press Alt+F1 to drop into a console.
4. Login with user root and blank password (just hit enter when prompted for password).
5. Change directory: cd /usr/lib/vmware/weasel/util/
6. Set permissions to allow any user to modify the install script: chmod 777 upgrade_precheck.py
7. Copy file to edit as it didn't like me editing it live: cp upgrade_precheck.py temp.py
8. Edit the file: vi temp.py
9. Edt the line with "MEM_MIN_SIZE" you can use / to search in vi.
10. Press i to enter insert mode in vim.
11. Change 4 * 1024 - 32 to 2 * 1024 - 32
12. Press Esc to exit insert mode on vim.
13. Type :wq to write the changes to disk and close vim.
14. Copy the file back over the original: cp temp.py upgrade_precheck.py
15. Locate the installer proccss ID: ps -c | grep weasel
16. Kill the process using its ID: kill PROCESSIDHERE