File size very large for a single slide - is this normal?

I'm working in Captivate 8 with .cptx file ~500MB in size. I wanted to send an example of a click box (including hint text, size, and placement) to a colleague. To make it easy for him, I hoped to send a single slide with that interaction, so he could copy and paste.

I saved the file with a new name, and then I deleted all of the other slides. The size of the new file was still almost 400MB! I then deleted all unused library items and the link to a .ppt presentation. This reduced the size to just over 300MB.

Am I missing something? Is this normal?