There is no limit, however, there is a daily quota. Hypothetically the entire circulating supply can be bridged, though this likely will never happen since there will be strong use cases to use the tokens on either network.
|Daily limit POA -> POA20||3,000,000 POA|
|Daily limit POA20 -> POA||1,500,000 POA20|
|Maximum per tx POA||1,500,000 POA|
|Maximum per tx POA20||1,500,000 POA20|
|Minimum per tx POA||300 POA|
|Minimum per tx POA20||750 POA20|