What is the pixel density of both machines? For example, if your MacBook has a pixel density of 227 pixels per inch (PPI) and your monitor has only 96 PPI, a 100px brush will not have the same dimensions on both devices.
Why? Because on the MacBook, 100 pixels will be less than half an inch (approximately 0.44 inches), while on the monitor, 100 pixels will be exactly one inch. This difference in pixel density will result in the brush appearing larger on the monitor than on the MacBook.
Additionally, in the Units & Rulers section of your software's Preferences, you can adjust the Screen Resolution setting to achieve a more accurate and consistent preview.
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