Subtraction.
Strike the minuend positive and the subtrahend negative, see page 11.
A row of cut offs by which the carrying of any column can be stopped at will, have been put in front of the keys. They are for use in subtraction and in correcting mistakes. Do not try to subtract a number from one smaller than itself; for instance in the example, 2114-18; as 18 cannot be substracted from 14, push back the cut off just above the third column and strike 017 according to the red figures.
In examples like 183-45, push back the cut off above the second column and strike 44 on the red figures.
Example: Find the value of 4286-262. After striking 4286 positive strike 262 negative while holding back the cut off between the third and fourth columns. The red figures to be struck are, therefore, 2, 6, and 1. The number 4024 will be then indicated on the register, as the remainder.
Correcting Mistakes.
One seldom strikes a wrong key without noticing it before completing the stroke, and can immediately rectify the mistake by striking a key in the same column which is the same distance from the other end of the column while holding back the proper cut off. Thus: If the 8 key in the thousands column is struck by mistake, it being the second key from the back end of the column, strike the second key from the front end of that column.
If several keys are struck by mistake, simply subtract the amount which they represent and proceed as though no mistake had been made. Thus: Suppose 1783 had been struck, strike 1782 according to the red figures in the same columns while holding back the proper cut off, and the amount on the register will be the same as though no mistake had been made.
