@anneshy I think what they’re doing here is 3% annualized equates to 0.25% per month. Since it’s a 3 month promo you basically earn 0.25% for the first 3 months and then it drops down to whatever the regular rate you’re seeing.
So if you start with a principle of $1000. After 3 months you are left with, which works out to (1000 x 1.0025) + (1002.5 x 1.0025) + (1005.006 x 1.0025) = total increased investment after 3 months.
The figures on the left side on the brackets are the initial principle, and then the new sum after month 1 and month 2.
Here’s a calculator which explains the calculations a little more clearly.
Edit: It’s late here - I thought you said 3% is the annualized rate not 2.3%. The above still applies you just have to plug in 2.3% as the annualized rate and release the same exercise.
@anneshy Please do yourself a favour and look into investing this money in the stock market where you can get far better returns. The big banks give you crap for TFSA when, for example you could put your knee into something like VFV which has reliably returned over 8%.
Don't use your TFSA literally as a savings account, that was never the actual intent.