Fifty kilobytes is the most common upper limit on Indian government and exam forms, usually paired with a 20 KB minimum for the photo. It is also enough for a crisp profile picture on any app and for logos in email footers. The tool keeps the pixels when they already fit and only shrinks them when it must.
At 50 KB you can expect about 550 to 700 px on the long side. The exact number depends on how much fine detail the image has: skies and plain walls compress well, foliage and fabric don't.
Tip: For a 20 to 50 KB requirement, set Min (KB) to 20 under More options so the file is never rejected for being too small.