When making changes in Act! and syncing to the device (or back to Act!), Handheld Contact has some character limitations (including spaces) that must be met.  Please see below.

Syncing from ACT! to device:

Activity Regarding Field - 256 characters.
Activity Details Field - 1985 characters before truncation - HHC will show "(Truncated)(RO)" - 'RO' meaning Read Only.
Notes - 5000 characters.
History Regarding - 256 characters.
History Details - 4985 Plus HHC will show "(Truncated)(RO)" - 'RO' meaning Read Only.
Contact Character Field - 450 character MAX due to ACT! limit.  Go to Tools - Define Fields to determine field max limit.
Contact Memo Field - 236 characters before truncation - HHC will show "(Truncated)(RO)" - 'RO' meaning Read Only.
Contact Location Field - 128 characters.

Syncing from device to ACT!:

Activity Regarding Field - 256 characters.
Activity Details Field - 2000 characters.
Notes - 5000 characters for iOS and Android devices.
History Regarding - 256 characters.
History Details - 5000 characters for iOS devices, Android devices.
Contact Character Field - 450 character MAX due to ACT! limit.  Go to Tools - Define Fields to determine field max limit.
Contact Memo Field - 236 characters.  Handheld Contact on device does not limit what can be entered into the field but if you exceed the max, the contact changes do not sync into Act! and no errors are produced.