The lower toolbar includes some very important general settings including the decimal places. But lets start from left to right:

NUM:

this button shows if the Numlock key is pressed or not, this is important for the 10-key keypad users. You may even change the numlock-key by using this button in the toolbar.

Keys:

this button shows or hides the calculator keys area.

DEC.:

use the decimal places box, to set the number of decimal places. You can change the decimal place setting of any calculation series at any time. You can set the number of decimal places using the mouse or the keyboard, use CTRL+1 to CTRL+6.  The minimum number of fixed decimal places is zero; the maximum is 6. Use F (float) to activate floating decimal places.

DeskCalc waits 1 second after the last arrow button click, to be sure you are finished, and then redisplays the numbers in the calculation series with the new number of decimal places.

DeskCalc recalculates calculated numbers.  If the new decimal place setting is a fixed number of decimal places, it rounds calculated numbers to the new number of decimal places.

RND:

With RND (for rounding off), if unchecked, the decimal places are
rounded with 3 different options:

• 4/5 Rounding, Round Half Up
• Round Ceiling
• Round floor

If the function is not activated the results are calculated according to the digits indicated in the corresponding list, however without rounding off.

AM:

In the case of activation of the automatic decimal place separation AM the adjusted number of places is separated automatically during the input from decimal places.