Certified GKH Gardening Expert
Oh boy... Even when used properly, the half life of this product is 30 to 60 days. It could be up to two months before the ground is suitable. This is a selective herbicide, that doesn't usually effect grass. Under no circumstances should it kill grass unless it is used way out of proportion to the label.
Follow all instructions on the packaging when it comes to toxic chemicals such as this, since they are likely to cause issues with runoff in groundwater, and getting into sewer systems.
In the US, these particles can be found in our water supply on occasion, signaling that it does not get destroyed completely by chemical or filtration systems.
Please take care in following all instructions on the label when using dangerous chemicals, and hopefully you can reseed in a month or two.