Trying to understand DICOM headers

I am currently taking a CIIP bootcamp course and I am having some trouble understanding DICOM headers. They gave us an image of a CT IVP and what an example DICOM header sheet would look like. here were some of the exercises they gave us Use the values in 0028,0010 and 0028,0011 to calculate the image size in pixels Now use the value in 00280100 to calculate the byte size of the image (ignoring the header). Then use the number of images in the series to calculate the size of the series. Using 0028,0030, what is the size in cm of an image? What are the smallest and largest value that an image can have (0028,0101) (0028,0106)? Knowing that displayed images can have negative values, how is this accounted for in the header? Considering tag group 6000, what are the characteristics of the overlay for CT?
what exactly are group tags and elements? I looked online and it said there are 16 bits per pixel. if 8 bits = 1 byte, 16 bits = 2 bytes = 1 pixel. rows (217) x columns (431) of the CT image is 93,527 pixels. so does that mean there are 187054 bytes for the CT? I am still having trouble understanding what the negative values are in the displayed image. I also don’t know what does the video mean by the overlay tag group.
​ https://preview.redd.it/48aj9lmtahw51.png?width=725&format=png&auto=webp&s=d2e82e564e287a71b70b03fb0fdc83ecfbf70866 https://preview.redd.it/v2qhwqmtahw51.png?width=705&format=png&auto=webp&s=e32da84e7d2dc745f6524a4ba40933b63a03f177 https://preview.redd.it/hlyu6qmtahw51.png?width=701&format=png&auto=webp&s=d6cec2a7bf9b7c67f30e0538c37ddd1f95761d7a https://preview.redd.it/g4yl8ymtahw51.png?width=713&format=png&auto=webp&s=6861d1bd9f1be14799396b79c39c57de81eaee07
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