Hi James thanks for reaching out and happy to help,

With Autoinvest, you can think of the % targets set for your shares as the goal that Autoinvest will aim to achieve for your portfolio. Therefore with every round, Autoinvest will make a fresh calculation as to which investments need to be made to best reach these goals. If the rebalance strategy is selected, it will calculate based on shares you already own, which ones need topping up to reach those % targets.
As you have selected Lowest share strategy (single below weight) at the time of Auto invest it will invest in the one asset that is the lowest weighted share (furthest away from its target %) in your pool of assets. This allows you to balance your portfolio over the long term without the need to buy multiple shares.
If you would like the rebalance option for Autoinvestment Allocation strategy you will need to make the changes by heading to Automate on your Pearler account and clicking the green arrow to edit the allocation strategy