Num lock. The Num Lock key exists because earlier 84-key IBM PC keyboards did not have cursor control or arrows separate from the numeric keypad. Most earlier computer keyboards had separate number keys and cursor control keys; however, to reduce cost, IBM chose to combine the two in their early PC keyboards.
The most common rule. The most common and frequently used rule for writing numbers in APA style is determined by whether the number is under 10. All those numbers should be written out in word form, such as four or seven. A number 10 and above is written as a numeral, such as 10, 17, 233.
However, instead of the index being positive (in the above example, the index was 3), it will be negative. The rules when writing a number in standard form is that first you write down a number between 1 and 10, then you write Ã 10(to the power of a number). This video explains standard form: