After connecting any channel to Multichannel, all stock changes must be done from Multichannel.
If you make stock level changes to any connected channel away from multichannel, they will be overwritten.
Operating like this is the only way to make sure that your stock numbers are consistent and accurate over all connected channels.
How to change stock level in Shoplo Multichannel:
Go to products > inventory > and click 'choose action' next to the product you want to change, then click variant details > quick edit
and type in the new quantity.
Go to products > Inventory > Select the products of that you want to change the quantity of.
Slide the button to 'Set' to set the quantity to a certain number or 'Add' to add a certain number more.
You will see a preview of how it affects stock levels.