Transitions from the current value to the current value plus the timeline value. No change is made before the first frame (the current value is kept until the first frame).

Add is intended for animations layered on top of others, not for the first animations applied. Properties set by additive animations must be set manually or by another animation before applying the additive animations, else the property values will increase each time the additive animations are applied.

Transitions from the current value to the timeline value. Before the first frame, transitions from the current value to the setup value. Timelines which perform instant transitions, such as DrawOrderTimeline or AttachmentTimeline, use the setup value before the first frame.

First is intended for the first animations applied, not for animations layered on top of those.

Transitions from the current value to the timeline value. No change is made before the first frame (the current value is kept until the first frame).

Replace is intended for animations layered on top of others, not for the first animations applied.

 Transitions from the setup value to the timeline value (the current value is not used). Before the first frame, the
                      setup value is set.