Considered as supply or not

No....
GST Applicable on advance is not treated as supply. Actually the liability to pay tax on goods or services are prescribed in Section 12 & 13 of CGST Act
Section 12 of CGST Act
Time of Supply Goods : Advance received against supply of goods no GST is applicable as of today . This provision was put in abeyance for registered person whose aggregate turnover not exceeding 1.5 crore other than composition dealer , vide Notification 40/2017 CT ef 13/10/2017, then Vide Notification 66/2017 ,e.f 15/11/2017 this benefits was extended all other registered person .

Section 13 of CGST Act :
Time supply of Services : Advance received against supply of Services, GST is applicable.


Note : Section 15(2) did not Prescribe GST on advance Reced.

This provision is applicable to service at present now