You can select the quality at which you intend to record using the bit depth selector and the sample rate selector. The higher the values, the better the quality of the recording and the more disk space this will use. In practice, this will also be a tributary of the recording equipment you are using. Most sound interfaces these days can record at 24 bits and up to 48000 Hz (48 kHz). More professional sound interfaces will allow you to record up to 192000Hz (192 kHz). Above this is rare although 32 bits/384000Hz (384 kHz) sound interfaces do exist, good luck finding them for studio use !
By default, the recording time is fixed (green arrow), that is, you set the amount of time you wish to record and the number of tracks you are recording (2 for stereo, 7 for surround, 16 for a small group, etc.), and the calculator will work out how much disk space your recording will occupy.
You can change to fixed disk space by clicking on the grey arrow below the green one and it will change to green to indicate that now the disk space is fixed. You can now enter the amount of disk space you have available and the number of tracks and quality of your recording and the calculator will tell you how long you will be able to record for before your disk is full.

The results of the calculation are shown at the bottom of the display.
You will also find an indication of the transfer rate of the data recorded, which can guide you in the choice of the hard drive you are to use for your recording. SSDs (solid-state drives) will give you much better performance than mechanical hard drives and are less fragile to knocks and drops than their mechanical counterparts, but at the time of writing, are considerably more expensive than mechanical hard drives for an equivalent amount of storage space.