Why did my clay get split into two lines in my shopping cart?

If you are reading this, you are likely almost as frustrated as I am.  We have had this issue for some time, and it has taken me probably around 6 months just to get the folks at Big Commerce (the platform this site runs on) to even understand what I am saying and try to look at the issue.  My support ticket has been closed several times and I have to keep reopening it and starting at the beginning again.  Today I finally got an answer (not really a resolution), but I at least understand why this happens, so that helps some, and maybe it will also help you.  The important thing to note is that the pricing is correct, and the total amounts should be correct.  It's just irritating that it splits your order up.  I'm sorry.  They have transferred my problem to a "feature request."  I'm not holding my breath that it will get fixed anytime soon....  Here's the full explanation for you, straight from the engineers.

This is Pepe with the Bigcommerce Product Support Engineering team. I am the agent currently reviewing this case. This case was escalated to to review reports of promotions splitting into multiple lines on cart page when a tiered promotion is triggered.

I was able to review the replication steps as well as replicate the issue myself: 

Through additional research, the functionality above is expected when working with promos. This refers to the additional line item presented for the promo items. This process occurs as seen above due to rounding.

For example, If an order was $20 and had a discount split equally between the quantity of products. Say in an order with a quantity of 4, this is done easily ($20/4 = $5 off each product).

However, In a quantity of 3, there is an issue ($20/3 = $6.6666667). The system has to account for this extra penny so one item gets rounded up a penny in price, while the other products round down. 

This is the current expected behavior, yes it may visually not be what you're expecting. However, the pricing is correct there following this logic. 

Now, we do have an engineering ticket open internally which aims to review this currently functionality in order to improve and set the discount on the line item itself, without having to split into a separate line. At the moment this is a Feature Request ticket and is known as CHECKOUT-6311. 
This ticket is a feature request and not a bug as our system is working as it was designed to. Yes this approach may not be what everyone is pleased with, however, that is where the feature request ticket comes into play.

In favor of the engineering ticket, I will be closing this case. Please Note: When a support case is associated with an engineering ticket, the support case is considered resolved. A resolution for the issue will come from the team working the linked engineering ticket. This will come in the form of a separate ticket closure email confirming the fix.

Support cases are not left open once an engineering ticket is created, and we do not provide ongoing communication about the status of engineering tickets through support cases. This is because engineering tickets can take varying amounts of time to be investigated and resolved.

If it is necessary/desired to get an update on the status of any particular engineering ticket, feel free to contact BigCommerce Support at 1-888-699-8911. For managed Enterprise merchants you may contact support or your Customer Success Manager.

I appreciate your patience and understanding. Thank you for contacting Bigcommerce. Enjoy the rest of your day.