What is the limit on data.com records that can be added to salesforce?

Data.com Prospector user licenses let users search Data.com for accounts and contacts, and add them as records to Salesforce. Users can be assigned one of two types of licenses—Data.com User and Data.com List User— and each type has its own characteristics.

REQUIRED EDITIONS
Available in: Salesforce Classic (not available in all orgs)
Available with a Data.com Prospector license in : Contact Manager (no Lead object), Group, Professional, Enterprise, Performance, and Unlimited Editions

IMPORTANT You need to assign a Data.com license directly to a user in order for that user to add and export files from Data.com.
Data.com User
Data.com Users get a limited number of account, contact, and lead records to add or export per month. The default number of records per licensed user is 300. The record addition limit for each licensed user refreshes at midnight on the first of the month (based on the time zone of the organization) regardless of your contract start date. Unused record additions expire at the end of each month, do not rollover to the next month, and are not refundable. You can select the Data.com Monthly Addition Limit for each user. This is the number of account, contact, and lead records the user can add each month. You can select up to the organization limit for any user or all users, but once the organization’s monthly limit is reached, users won’t be able to add more records.

EXAMPLE The sales division of Universal Telco has 14 sales reps, and they purchase 20 Data.com Prospector licenses, each of which has a record addition limit of 300. This means that Data.com Users within the organization can add as many as 6,000 records per month. The Universal Telco administrator distributes the Data.com Users’ monthly record addition limits as follows.Ten of the sales reps have limits of 300 each
Two of the sales reps have limits of 500 each
Two of the sales reps have a limit of 1,000 each
Data.com List User
Data.com List Users get a limited number of account, contact, and lead records to add or export per month. Unused record additions expire at the end of each month and do not rollover to the next month. After the monthly limit is used, List Users draw record additions from a pool that is shared by all List Users in the organization. Unused pool additions expire one year from purchase. Only Data.com List Users can draw from the organization’s pool limit. If a Data.com User wants to draw from the organization’s pool limit, you need to change that user to a Data.com List User.

EXAMPLE The marketing division of Universal Telco has four marketing reps. Each rep has a Data.com Prospector license and each is a Data.com List User. Universal Telco purchases enough monthly record additions so that each Data.com user has a monthly default limit of 300 records. The company also purchases a record addition pool of 5,000 records. This means that after each marketing rep uses his monthly limit, he can start using the pool limit. Together, all four marketing reps can add 5,000 records from the pool. One rep might add 2,500 records, leaving 2,500 to be added by one or more of the other three users.