The number of products in the feed seems to be less than the products made available to feed?

There could be a number of reason for this

• The “Action for Out Of Stock variants” option you selected maybe in action. The option allow you to include or exclude the out of stock variants. For example, if you chose to exclude OOS variants and and all variants of a product (or the default variant of a single-variant product) is out of stock, that product will not appear in feed.
• You may have choose a variant option filters. For example, if you selected to include only Black variant of a shirt in feed, other products which does not have a Black variant will not be included.
• Unpublished products are NOT included in feeds. Most of the time this is the reason why the number of products in feeds are less than the available products. Unpublished products are only visible to store users, therefore they need to be excluded from feeds.