[SOLVED] can someone explain how she found the phase shift

a certain mass is supported by a spring so that it is at rest 0.50m above a table top. The mass is pulled down 0.40m and releasted at time t=0sec, the highest position of the mass is 0.90m. It takes 1.20s for the mass to return to the low position each time. Graph the function and find its height at 0.70s.

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i understand everything on the note except where she determined the shift...

from the question i know that the initial height is at 0.50m at 0s ... and the max height is 0.90 at 0.6s ...

can someone just explain it a little more (Angry)