Help with glow app period calculator

jolam

My partner came on her period last month February 18th. <a href="https://play.google.com/store/apps/details?id=com.glow.android">Glow app</a> is saying she’s now 3 days late but her cycles every 28 days so we thought she is due on today 18th March.

Is it right that she’s 3 days late?