What is Span Value from Span?

They both have the same meaning in most cases. Usually used in the context of setting the range of operation for some device or measurement where you can adjust the zero point (sometimes called "offset") and you can adjust the high end of the range called span or span value (sometimes called "gain").

These terms came about because in the analog world, you would adjust the offset to the instrumentation amplifier to set your zero point (with zero input) and you would adjust the gain of the instrumentation amplifier to capture the upper end of your measurement range (with the maximum expected value applied to the amplifier).

You may find this reference from what used to be called Instrument Society of America to be useful in how the concept span is used in the context of calibration.

https://www.isa.org/pdfs/calibration-principles-chapter1

Good luck with your quest.

Take an example for a temperature range of 50-250°C.
The span value is 250°C.
The span is 200°C (250 - 50 = 200)

..."The HTML <span> tag is a generic container for inline elements and content. This allows you to apply styles and other attributes to the content within the <span> element.

The element itself doesn't represent anything other than its children. It is similar to the <div> tag, except that the <div> tag is used for block-level content (as opposed to inline content that the <span> element contains).

The basic tag is written like this <span class=""></span> with the grouped content between the opening and closing tags. In this example we are using the class attribute, which can be used to apply styles to the contents of the <span> element. The value provided here would need to be the name of a CSS class. See below for more information about attributes that can be used with the <span> element."...

http://www.html.am/tags/html-span-tag.cfm

Semantics.

Sorry for being a Yank to say this, but "quite".