The TA rise is from the pH up, not the borax. Your pH must have been rather low, your fill water must be on the acidic side. You do want to get that up to at least 7 before you start SLAMing. Also pH up and soda ash are the same thing, sodium carbonate. You will also find it in the laundry aisle next to the borax, labeled washing soda. Whatever you have on hand will be fine to bring your pH up at this point, your TA is ok but can be raised a bit more without problems.
Keeping your FC around 7 before the SLAM will help keep things from getting worse but don't raise it above 10 while adjusting your pH. The pH test is not accurate when FC is over 10. Remember too, you need 9 bottles to start, you then will need to test every few hours and bring the FC back to SLAM. If you need 9 to start then you should grab no less than 20 so you don't run out right away.
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