The "Invested in store" stat line keeps track of how many stores you have invested in using the Investor Perk from the Speech Skill tree. Investing in a store grants the merchant in question a permanent 500 gold increase to their gold inventory, meaning you can sell significantly more goods to them before they run out of gold.

Investing in Stores

Investing money in stores is a way for merchants to have more money to use in sales. You can only invest once to each store. In the stats it keeps tracked of the stores invested.

How to Invest

You will need to have your Speech skill to 70 or above. One way to increase this skill is to talk to Ungrien at the Black briar Meadery in Riften and talk to him about Maven and use the persuade option. Use this dialogue for many times. This only works below Patch 1.9. Another way is to make strong armor, enchant them, improve them, and sell them to merchants.

Now once you have 70 Speech, you'll need to spend a perk called Investor. This will allow you to invest in a shop for 500 gold. You might want to spend the master trader perk once the skill is at 100 so merchants have 1000 more gold. There is a glitch when at the Riverwood Trader when investing in the shop, it will add 10,000 gold instead of 500. Fixed by patch 1.9.