How rows and columns can have implicit dimensions?

/* Keyword values */
grid-auto-rows: min-content;
grid-auto-rows: max-content;
grid-auto-rows: auto;

/* <length> values */
grid-auto-rows: 100px;
grid-auto-rows: 20cm;
grid-auto-rows: 50vmax;

/* <percentage> values */
grid-auto-rows: 10%;
grid-auto-rows: 33.3%;

/* <flex> values */
grid-auto-rows: 0.5fr;
grid-auto-rows: 3fr;

/* minmax() values */
grid-auto-rows: minmax(100px, auto);
grid-auto-rows: minmax(max-content, 2fr);
grid-auto-rows: minmax(20%, 80vmax);

/* multiple track-size values */
grid-auto-rows: min-content max-content auto;
grid-auto-rows: 100px 150px 390px;
grid-auto-rows: 10% 33.3%;
grid-auto-rows: 0.5fr 3fr 1fr;
grid-auto-rows: minmax(100px, auto) minmax(max-content, 2fr) minmax(20%, 80vmax);
grid-auto-rows: 100px minmax(100px, auto) 10% 0.5fr fit-content(400px);

/* Global values */
grid-auto-rows: inherit;
grid-auto-rows: initial;
grid-auto-rows: unset;

/* Keyword values */
grid-auto-columns: min-content;
grid-auto-columns: max-content;
grid-auto-columns: auto;

/* <length> values */
grid-auto-columns: 100px;
grid-auto-columns: 20cm;
grid-auto-columns: 50vmax;

/* <percentage> values */
grid-auto-columns: 10%;
grid-auto-columns: 33.3%;

/* <flex> values */
grid-auto-columns: 0.5fr;
grid-auto-columns: 3fr;

/* minmax() values */
grid-auto-columns: minmax(100px, auto);
grid-auto-columns: minmax(max-content, 2fr);
grid-auto-columns: minmax(20%, 80vmax);

/* fit-content() values */
grid-auto-columns: fit-content(400px);
grid-auto-columns: fit-content(5cm);
grid-auto-columns: fit-content(20%);

/* multiple track-size values */
grid-auto-columns: min-content max-content auto;
grid-auto-columns: 100px 150px 390px;
grid-auto-columns: 10% 33.3%;
grid-auto-columns: 0.5fr 3fr 1fr;
grid-auto-columns: minmax(100px, auto) minmax(max-content, 2fr) minmax(20%, 80vmax);
grid-auto-columns: 100px minmax(100px, auto) 10% 0.5fr fit-content(400px);

/* Global values */
grid-auto-columns: inherit;
grid-auto-columns: initial;
grid-auto-columns: unset;