In this case we only needed 1 byte for each variable so only 1 was reserved for each. Also you will notice that everything lines up vertically. This is only for readability for the programmers sake of clarity. The rule that the assembler uses is that at least 1 space must be between each part of the line. Plus by using short names, more space is left for the comment field.
Comments are very important.
When you initially write a program, the tendancy is not to write much in the comment field because you're in a hurry. But if you have to come back to it a few weeks later, it's much easier to understand what you've written if you've taken the time to write good comments. Also good comments help in debugging. In this example, we reserved two bytes and stored a 2 in each one. Now the accumulator has a 4 in it, and first and secnd still have a 2 in them.