How much should I deduct from my tenants security deposit. The tenants parked on the lawn. The damage is related to the lawn?

My tenant leaves in about a month. Yesterday, I noticed that they have been parking on the lawn, which has caused the grass to turn to dirt. The area that I will need to re-sod is around 600 sq ft. I plan on doing the work myself, but I m unsure of how much to charge them. A sod cutter, dump fees, and pallet of... show more My tenant leaves in about a month. Yesterday, I noticed that they have been parking on the lawn, which has caused the grass to turn to dirt. The area that I will need to re-sod is around 600 sq ft. I plan on doing the work myself, but I m unsure of how much to charge them. A sod cutter, dump fees, and pallet of grass will cost around $340. However, I don t know how much to charge them for my labor/time. Any help would be appreciated.

I live in Florida, btw.
Update: Their security deposit was $1250 and I am considering keeping the whole thing.
Update 2: I'm not trying to steal anybody's money. My yard has been TRASHED. I explicitly told the tenants not to park on the lawn (it's in the lease as well). I'm simply trying to figure out how to go about getting my house ready to rent again. Thanks to everyone who left CONSTRUCTIVE answers.
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