CSS max-width has inaccurate pixel precision

I have an issue with max-width media rule. I test to hide the elements on different max-width values and the behavior is inconsistent. I have tested 4 scenarios varying in the screen width.

• Scenario 1: Screen width is 638px: This matches my expectation.
• Scenario 2: Screen width is 639px: This is wrong! I expect column639 still to be hidden!
• Scenario 3: Screen width is 640px: This matches my expectation.
• Scenario 4: Screen width is 641px: This matches my expectation.

Question:

What causes the pixels inaccuracy in the Scenario 2 and why is 639px value treated differently than others?

Reproducibility:

Strangely, it cannot be reproduced everywhere (resize the window to the width of 693px:

• Google Chrome: I can reproduce, (86.1.6938.200, 64-bit)
• Mozilla Firefox: I can reproduce, (87.0.4280.88, 64-bit)
• JSFiddle: I cannot reproduce (all scenarios as expected): https://jsfiddle.net/vop23ang/
• CodePen: I can reproduce (all scenarios as expected, you need to Change View to resize horizontally): https://codepen.io/nikolas-charalambidis/pen/YzGYPGE

Code:

<!DOCTYPE html>
<html>
    <head>
        <meta name="viewport" content="width=device-width, initial-scale=1">
    </head>
    <body>
        <h1>max-width issue</h1>
        <div class="column column639">
            <h2>Column 1</h2>
        </div>
          
        <div class="column column640">
            <h2>Column 2</h2>
        </div>
    </body>
</html>

.column {
    width: 100%;
    background-color: cyan;
}

@media screen and (max-width: 639px) {
    .column639 {
        visibility: hidden;
    }
}

@media screen and (max-width: 640px) {
    .column640 {
        visibility: hidden;
    }
}

Scenarios:

Scenario 1: Screen width is 638px:

Scenario 2: Screen width is 639px:

Scenario 3: Screen width is 640px:

Scenario 4: Screen width is 641px: