Hey @np604 !
A cap of $150 was scheduled to happen in December of 2018. Due to unforeseen circumstances, this date is postponed to a future date in 2019. Once the cap is effective, Prepaid account balances will be capped at $150. This means that your account will have a maximum balance of $150.
For now, you can go ahead and top-up even if it goes to $190, just try to use up the $40 extra so that you aren't affected once a cap comes into effect. We'll have more news to share later on this year.
Hope this helps!