SigParser is configured by default to a low number of daily API requests so your other Salesforce applications don't get starved of requests. SigParser can sometimes use a lot of API requests when doing large sync jobs.
Most organizations have 15,000 + (1,000 x # of users) allowed per day. Unlimited or Performance editions get 15,000 + (5,000 x # of users). If limit is hit the remaining work will be done the next day. You can purchase more requests per day from Salesforce.
The more Salesforce users you have the more API requests your organization will have.
You can configure the daily API request limit number in SigParser:
Login to SigParser
Go to Connectors
Click the Salesforce connector name
Select Export Options > Export Rules > Advanced Settings
Set API Request Limit