The settings in thist field has an autocomplete which chooses the first filtered option in the list so when you tab out of the field, the autocomplete item is chosen. If you type in "M" and tab out, it chooses "March". Use the arrow keys or the arrow button to choose. Or type in the first few letters. The drop down doesn't appear unless you click the arrow button. This makes it faster and ideal to select when the list is small and well known.
The Enter key can be used to toggle the drop down list on or off. Type in the first few characters to limit the selection. Up arrow can take you to the bottom of the list. This makes it very fast to select especially when the list is in a known order.
For a larger list such as a Country list, filtering is set to after 1 character is typed. Use the arrow keys or the arrow button to choose. Or type in the first few letters. THe autocomplete option is on here so that it's fast to select.