I researched this too-it's a hypothetical point of a chart same as Part of Fortune is. Here's the link with a calculator:
https://horoscopes.astro-seek.com/part-of-fortune-lot-of-fortune-online-calculator
A breakdown of the Lots concepts:
http://www.astrology-x-files.com/x-files/arabic-parts.html
More info! https://www.astro.com/astrology/in_fortune_e.htm
But yes, from what I could find, it seems that not much is known about the Lots except for the Sign that they fall under. Sounds to me like an interpretation of the life theme, how it's expressed, and where in life it's shown. The key here is that under the Lot of Eros, it must be mutual exchange between both parties.
For example, a Lot of Eros under Aries in the 5th House can be interpreted as this is how the native will always find help, support, friendships and lovers: through passionate interests, hobbies, and recreations.
Hope this post wasn't off course and helps!