graphic designer sometimes must adjust the spacing between letters so that the results looks right to them. this is called
http://papress.com/thinkingwithtype/text/kerning.htm
The practice you're referring to is called "kerning." Kerning is the process of adjusting the spacing between individual letters in a word or phrase in order to achieve a visually pleasing and balanced outcome. During the design process, graphic designers often make these adjustments based on their subjective judgement and visual perception.
To understand how to adjust letter spacing effectively, graphic designers typically consider the overall composition, readability, and aesthetics of the text. Kerning ensures that there is consistent spacing between letters, eliminating any awkward gaps or cramped areas that might disrupt the flow and legibility of the text. By carefully adjusting the kerning, graphic designers can achieve a balanced and harmonious look in their typography.
In digital design software such as Adobe Photoshop, Adobe Illustrator, or other design tools, there are specific kerning features available that allow designers to modify the spacing between letters. These tools provide various options to manually adjust the letter spacing, as well as automated features that suggest or apply default kerning values. Designers can also use their own judgment to adjust the spacing based on their understanding of the design principles and the desired visual effect.