When you sign up for a free trial in Keyword Chef, your account is credited with 1000 free credits.
There are limits to your free trial account:
Maximum of 30 SERP lookups
Get all SERPs feature is not available
There is no time limit to your free account. Credits never expire.
When you purchase any paid plan, you will be able to keep your free credits and get access to the Get All SERPs feature. There will be no limit to the number of SERPs you can look up.